Your two cats are best friends. They play together, groom each other, and sleep curled up with each other. Then one day, you take one to the vet’s for a check up. When you return from the clinic, instead of receiving a warm welcome, the cat who stayed home hisses and attacks the other cat. Your two former best friends have turned into sworn enemies, and your formerly peaceful home has turned into a battle zone.

Aggression between cats is always a distressing problem for the cats and the humans involved. Whether it’s play aggression, petting aggression, or redirected aggression, dealing with feline aggression is stressful and requires commitment, staying power, and the help of experts such as your veterinarian and/or a feline behaviorist.

The cause of on-recognition aggression is not entirely clear, and the bad news is that it’s not easily fixed.

Possible causes of non-recognition aggression

  • The returning cat smells different. He may have absorbed smells from the environment at the veterinary clinic. If he had anesthesia, the drugs may have temporarily altered his body chemistry, which may also result in a different smell to sensitive cat noses.
  • The smell of alcohol or other medical smells may remind the cat who stayed at home of a negative experience.
  • The returning cat may have released his anal glands while he was in route to the vet’s, or at the vet’s. While this may seem simply be a stinky mess to us,  to the other cat,  it may signal fear and danger.
  • The returning cat may behave abnormally. If he hasn’t fully recovered from anesthesia, he may wobble as he walks. This may be perceived as a threat by the cat who stayed home.

Unfortunately, the attacks resulting from non-recognition aggression can be quite vicious, and can also be redirected at the humans in the household.

How to deal with non-recognition aggression

  • Never let the cats fight it out. Cats don’t resolve their issues through fighting.
  • Interrupt the aggression in a way that keeps you safe. Clap your hands, toss a toy, throw a blanket over the cats, or separate them by pushing a piece of carboard between them.
  • Try to herd the aggressor into a separate room and close the door. This gives both cats a chance to calm down. This can take several hours, and sometimes, days.
  • Don’t try to soothe the aggressive cats – leave him alone to give him a chance to calm down. An agitated cat may continue to be aggressive and redirect that aggression against the humans in the household.
  • Give the cats a chance to familiarize themselves with each others’ smells and sounds after they have calmed down. In severe cases, you may need to start a gradual reintroduction, as if they had never met before.

How to prevent non-recognition aggression

Nobody seems to know for sure how to prevent non-recognition aggression, but the following may help:

  • Make sure the returning cat has fully recovered from anesthesia or sedation before bringing her home.
  • Remove any veterinary odors from the returning cat. You can bathe the cat if this doesn’t add more stress, or use unscented baby wipes. Follow this by rubbing something with the cats’ regular scents on them, such as a blanket or favorite toy. Rub both cats with this item.
  • Keep the cats separated for a few hours to give them a chance to get used to each other’s sounds and smells.
  • Reward the cats with treats and praise once they interact in a friendly manner.
  • Use holistic remedies such as Stress Stopper for the cat who is going to the vet’s, and use Stress Stopper and Peacemaker for both cats once he returns home.

Some experts advise to take both cats to the vet together, even if only one cat needs veterinary attention. There is no evidence that this helps prevent non-recognition aggression, but it may be worth a try if this has been an issue for you in the past.

Photo by Feliciano Guimarães, Flick Creative Commons

81 Comments on Non-Recognition Aggression in Cats: A Case of Forgotten Identity

  1. To add, let’s put it this way: She’s fine with us, him (usually!) and other adults. Some she even fears, randomly, and hides from. Most she’s social and affectionate with. But no one is bringing small children or dogs here. That’s a rule. We have to lock her up, which she only tolerates for a long period if I’m with her, or it’s just huge risk for anything other than a large dog. And even then. It’s crazy to see her go from loving/charming/intelligent and hyper-social/vocal baby girl to psycho “you’re going to die” on whatever she doesn’t like. Never thought I’d see it on her own “brother”.

    • I can totally sympathise with cat lovers who have gone through these experiences. It took over a year fir me to find a solution to this dilemma.
      The aggression involved a large male cat towards a smaller longhaired female.
      The female was given a haircut to deal with some hair matting. She hated to be brushed and this seemed to be the only solution. When she came home there was big-time non-recognition, and the male cat who had previously only been friendly with her went into attack mode and this continued at every opportunity for months. Gradual reintroduction didn’t work even after the female cat’s hair regrew to normal. I finally had to resort to seperating them with one living upstairs and the other downstairs, and had a lattice door built at the top of the stairs. Then a serious medical emergency in my family meant I had to suddenly leave town for two weeks. A friend came in to feed the cats while I was away. In their loneliness they rebonded! When I came back they were meeting each other at the lattice without growling and clearly wanting to reconnect. They did with no further problems.

  2. I’ve witnessed it before in both cats (9 yr. old female and 14 yr. old male) to each other, be it a vet visit or groomer, and regardless of whether they went separately or together but I’ve never had to physically separate them for more than a few hours really.

    Now that older male had surgery (broken tooth + benign cyst removal) and spent a full day there, she’s been hellspawn with him. Not just a hiss when she sees him in our arms, which she does, but full on charge/attack with zero hesitation or provocation. Very aggressive. Now, she’s always been the “tougher” one, an outdoor rescue as a kitten. Never towards us (and I can easily interrupt her aggression towards him by picking her up without any fear she’ll turn on me) but she’s still the slightly more “feral” for lack of a better term. If she sees an animal outside, her instinct is more to attack than hiss and posture. First time she’s doing it to him though. He’s much bigger. They play together a lot, sleep together, always eat together etc. Sometimes play can get rough but they have boundaries and he’ll usually shut it down when it’s too much, chasing her away. We really never need to intervene. That wasn’t the case with our older (now, passed away) female. That was always hell we had to monitor.

    But I’ve never seen her like this and he’s too drowsy/confused (and has stitches on his back/side – so limps and needs to be monitored) to do anything about it except kind of panic and back up. We’ve both taken off work and other than a few “mistakes” of miscommunication in transferring rooms etc. where she’s managed to take a quickly interrupted run at him, we’ve kept it well under control. It’s been 48 hours now. He’s much less drowsy, reacting to her differently. She’s been up and smelled him while he was resting, and didn’t do anything at all, just smelled him and walked away. But she will still insta-charge if, say, he comes wandering in. We’re sleeping in separate rooms, me with her (she won’t stay with my gf for more than an hour but is fine spending a whole night with me) and her with him. Great.

    But my gf goes back to work (nurse, long shifts occasionally in 2 days) and I do too, though thankfully from home. So I’ll need to watch him for his stitches/cone etc. and lock her out which she will NOT like. I want to re-introduce them but it’s pretty terrifying and he’s not in a position to stand her down yet. Also, her claws are due. His are trim. They’ve never hurt each other but I think she would now. I’m fearing this will be a week+ particularly due to required separation due to instant attack vs. hissing/posturing. And of course he returns to the vet in 8 days for stitch removal and check-up, which will reset this. At least he’ll be stronger and more “ready” then. And we’re bringing her along to see, even though it’s never really helped in the past. Will also trim her claws very short to minimize any potential damage in a quick contact.

    Article helpful, experiences too… but all different. Wanted to share. And maybe someone adds further insight or a similar tale of SUPER aggression from one cat to another who needs to be protected more than ever due to open stitches/limp.


    • Thank you for sharing your experience, Greg. I know it’s distressing when this happens, especially when it doesn’t resolve quickly. Please keep us posted on how things are going.

  3. Has anyone noticed it’s always the females ? Mine is freaking out on my male too. They will be 12 years old in July same litter I got him shaved last week and she is freaking out.

    • I wonder if it’s an overload of many different animal sents the cat picked up on surfaces at the vet. I sometimes been to the vets with my cats and seen many cats, dogs, birds, reptiles, rabbits etc., at some places. If home cat gets bombarded with a bunch of new scents how does it decode who cat is that returned. I assume that even just one new scent of another animal would freak out the home cat, as does any new animal smell coming into house.

    • It’s not just females. I took my girl cat to the groomer for her first shave and shampoo (she was a matted long-hair). When she came back, the two older females were pretty chill, but her brother and sister both were quite upset. Her brother especially treated her like a complete stranger. They were littermates! I’m here because I want to see what else I can do (besides what I’m already doing) to bring the peace back.

  4. Hi. I have two 15.5-year-old sibling cats – male and female. My female cat has always been extremely skiddish while male cat is more relaxed. As described in the article, each time I would bring male cat to vet (regardless of whether female cat went or not), she would hiss at him for 3 days like he was the enemy, then get over it. In November, Lynx, the male cat got cancer and poor little guy had to get his front leg amputated. Leah, female cat, has hissed at him since she first smelled the cancer in November and until now, 3 months after amputation. I have read and tried most everything. Trading smells results in her completely avoiding the couch with towel (her petting place). Last time I brought towel close to her, she was so upset, she had like an asthma attack and couldn’t breathe for about 15 minutes. So I don’t do that anymore. Tried swapping rooms but they were both terrified. Used Feliway for 2 months. He now lives on the 3rd floor of the house and will not go downstairs because she stays on the 2nd floor. I have been leaving treats for her on the 3rd floor and now after 3 months she will go into the other 2 rooms on the 3rd floor, will occasionally eat some of his food, occasionally use his litter box on 3rd floor. But she will not go into master bedroom where he mostly hangs out. And she hisses at him when she sees him. By simultaneously giving them both treats, I have gotten to her move closer to him, now about 3 feet apart. So there is some progress. Right now, she sits on the landing of the stairs and eats treats, while he is 3 feet inside the master BR. But she will not step across the threshold even for treats or laser toy. I’m concerned bc Lynx is not getting exercise by going down the stairs (which he is capable of doing but is terrified of her). It breaks my heart that Lynx is probably lonely (but seems to have adjusted to amputation reasonably well). I’m doing the best I can. Any other suggestions? Thank you!

  5. We have 2 ex feral cats(siblings).They have been with us for about 3 years.
    Recently ,by an error on our part,the boy got out for about a week.We laced the area with a cocktail of treats,dry food and catnip .Lo and behold the boy(Shadow),came through the cat door.
    Shadow tried to get out again but,with petting and talking to,he settled down for the night.Actually,he spent most of the night on our bed,wanting attention.
    His sister ,on the other hand,hissed ,spat and growled at him when he was near,although she seemed more relaxed when there 6 feet or more between them.She did not come near our bedroom.
    This morning,Shadow is making chirping noises as if he wants to go outside again and Muse is still in growling mode.
    We have rubbed Shadow with a wet towel and we have rubbed a little catnip(which both cats love) on each cats coat—lets see what happens next—–

  6. I have two cats both stays and a pomp-mix who have been living together for over 10 years. I keep the cats indoors and have a porch I use to let them go out when they want to. An incident happened a day ago when on of the cats pounce and attacked the dog. I had to keep them apart. My dog does not engage the cats and keeps his distance as much as possible. My second stray is a sweetie who actually goes up to my dog. My second cat does not engage with my dog in any way so I was surprised as we all in my office the pets sitting around my desk when my second cat Missy attacked my dog she just went after him I had to get my dog out of the room. I thought after a day things were calming down but today at one point she went to find my dog who was in another room and hissed and approach him again. I yelled at her and since I was sweeping used the broom to let her know I meant business. She backed down a bit but I am afraid to leave them alone now. I have to watch to make sure she doesn’t go and find my dog who by the way does not fight back. I don’t understand the aggression against a dog my cat has lived with now for ten years.

    • You may need to separate your cat and dog and reintroduce them slowly and gradually as if they had never met before. Never yell at your cat, you’re only going to increase the aggression and risk her turning on you.

  7. I’ve been having some issues with my cat so this was an interesting read. My male cat Gizmo is about 18 months old and has been desexed. We got him as a 12 week old kitten when I was about 7 months pregnant. He is a 100% indoor/apartment cat but is allowed on the balcony. Most of the time he’s pretty good and he’ll sleep on my lap during the day and is generally friendly to me. But sometimes he will just snap and fully attack my arms or legs – might be a couple of times a week or a couple of times a day. He will latch on and wrap his legs around my arm and kick, scratch and bite (I’m totally covered in scratches and scars). I try not to shout and be agressive back to him but sometimes he’s latched on so tight it’s hard not to. Then I turn my back and try to ignore him which sometimes helps but if I walk away he will chase and go for my legs. It’s only me that he attacks in this way. After reading your article I suspect it may be redirected at me instead of my 13 month old daughter, as she can sometimes be a bit too rough and loud with him (we are trying to teach her about being gentle). Gizmo doesn’t always attack me after she has annoyed him though, sometimes it feels like he is jealous and sometimes it seems like a random attack. Is there anything you can suggest or recommend to stop him from attacking me?

    • It’s possible that it’s redirected aggression, but based on your description, I also wonder whether he’s just got a lot of excess energy, and attacking is his way of burning it off. I would try structured play therapy. Play with him two or three times a day, 10-15 minutes each session. Really get him tired out. Ideally, play with him before feeding him. See if that helps.

  8. My husband and I have two cats. One is female (mittens) and she is 3 1/2 and we have a male (mascot) who is 3 years. We got mittens first and had her for 3 months before we got mascot and it took a week to introduce them to each other before mittens accepted him. They have been inseparable since. After 3 years I thought nothing could part them. Well yesterday a stray cat walked into my schools gym during volleyball practice and i decided to take it home. I took it to the vet first and had it checked out. She got a good bill of health. We found out that it is female and is about 1 to 2 years old. We have the stray cat in a room by herself with all the wants and needs a cat could ask for and have kept her separated. My other two while curious still hissed at the door. This morning mittens started hissing and growling and actually attacked mascot. I am not sure what to do. My husband wants to give it a week or two with the stray and see if we can get them all to get along. I am just conflicted because I have never seen mittens act this way towards mascot and it really upsets me. I am wondering if I should just take the stray out of the question. Mascot and mittens are currently separated but when it comes to eating mittens acts how she always does with him (grooming, and very calm to each other) its when she is not eating that she gets aggressive. any thoughts?

    • This is redirected aggression rather than non-recognition aggression. Most likely, Mittens wanted to attack the stray, but since Mascot was the available target, she went after him. Here’s more information on redirected aggression: You may need to keep Mittens and Mascot separated and slowly reintroduce them to each other after this incident. At the very least, you’ll need to give Mittens time to cool off. Adding the stray into the mix is going to complicate matters. If you decide to keep the stray, you’ll need to restore peace between Mittens and Mascot before very slowly and gradually introducing the stray. A week or two is probably not going to be enough time to resolve this.

  9. I have a 3 yr old (male) and a 1 yr old cat (female) cat. They got along really well for almost two years. My sister took her cat (the 1yr old female) recently to nyc with her for 5 days. Ever since they got back my cat (3 yr old male) hisses at her. They’ve yet to actually fight but I’m afraid they will. What should I do?

  10. I recently got two kittens and they absolutely adored each other, the slept together and groomed eachother and played together. They were sisters and are are 7 months old and they just got spayed.
    When we brought them home they had a big fight in there joint cage and, one of the girls whenever she sees the other one hisses or grows and it breaks my heart. They will not sleep together or do anything together anymore, I have recognised it as this and I just want them to get along.
    Do you have any tips for making them my adorable two kittens again? Xx

    • I’m so sorry this happened to you, I know it’s distressing. Your best bet is to separate the two and introduce them very slowly and gradually as if they had never met.

      • If I may, I just went through this. It is heartwrenching. I cried a lot. I imagine you are too. I hope things are improving. It took me four weeks to get my cats back together, so don’t give up hope. Get some Feliway and have that going…it can take up to a month, but it really does help. Keep them separate until ALL the smell wears off. One of my cats holds odors for a really long time. It took a week for the vanilla smell to wear off to the point where I couldn’t smell her. And then probably a few days past that before the other cat couldn’t smell her.

        Then, if you haven’t already, set up meal times. Feed them on opposite sides of doors so that they get used to eating near each other (they can smell each other). When they are comfortable eating that way you can try opening the door a crack (hold it to keep it from opening to the point where they can get to one another) and back up how close their food dishes are. Slowly move them together. This could go as fast a one day or or take a bit longer. As they get comfortable, put up a baby gate so they can see one another better and move the dishes closer and closer. Then remove the gate (may have to back the dishes up, may not).

        The tough part comes in deciding to let them have access to one another. If things are going well and they seem to re-recognize each other, then put them in a room and play with both of them (having one person for each cat is beneficial). Site swap as well. Let each cat be in each area so they get used to the other’s smell. Even wipe them with a towel and then wipe the other cat to transfer the scent.

        Good Luck and don’t give up hope. It was a long month for me, but it was worth it. I was to the point of getting valium for them when things fell into place-so no meds. We are not perfect yet, but are 90% there. It does get better.

        Last bits of advice-stick to a plan. Don’t change things up every few days. And when introducing my cats, I found putting some tape on the floor where I put the bowls each day gave me a visual of how comfortable the cats were in each other’s presence…seeing the tape get closer and closer gave me a sense of accomplishment-which was important for my mental health.

        • Thank you for sharing your experience, Sarah. And that’s a great tip about using the tape to mark the spot where you put the bowls! I’m glad things are almost back to normal for you. It is a very distressing experience to go through.

  11. This article is very helpful. My two cats have lived together for 5 years (one is 11 years old and one is 5 1/2 years old.) While they have never been the best of friends, they co-habitated without problem and even played together occasionally. Till I took the older one to the vet for vomiting.

    When we came back, it was World War III. It’s been 4 days now and while they can eat in front of each other (baby gate between them) they have yet to be in the same room for more than 3 minutes without a some sort of aggression-either hissing or moaning/growling and one time -a knock down drag-out fight. . The first time I couldn’t get them separated and the older cat has a wound below her eye and is missing a claw sheath (She instigated that fight.).

    Usually it is the other cat who instigates and the older one responds at a much higher level. I can get the older one to play while they are in the same room, but younger one is clearly on guard.

    I’ve have a Feliway diffuser coming tomorrow and I’ve covered both cats in fish juice (the liquid from a can) and that helps slightly .

    I’m wondering if the vanilla trick will help. I’m wary of introducing yet another new smell.

    There is only me, so if I have to break up a fight, it is very hard. Plus it is hard to keep both cats occupied in the same room and being praised as I can only interact with one at a time-though I try my best.

    Any advice would be helpful. I want my happy home back!

    • You may need to slow the reintroduction down. Don’t let the cats be together in the same space yet. You may need to keep them in separate rooms for a few days and then slowly start over introducing them to each other. I’ve heard mixed feedback from vets about introducing another scent via the vanilla trick and would probably not do that at this stage. You may also want to consider adding Stress Stopper and Peacemaker from Spirit Essences I know this is distressing, but you can get your happy home back – just go very very slowly.

      • Thank you for the response. I still don’t have my cats together. I can feed them at a distance of 12 inches apart from each other with no barrier and with no issues. They both just eat. They even walk away when they are done. This has been going on for about 6 days now.

        I live in an apartment and the living/dining area are close together. But Isabel (young one) has become territorial about the dining table. If she gets under it, she will hiss when Sadie comes into view. Or if she gets on top of it, she will hiss if Sadie goes under it and then suddenly comes into view. They haven’t had this interaction in the last 6-7 days. I slowed way down on their contact time.

        Any advice for when it is time to let them in the same space to mingle? I’m afraid I won’t be able to stop a fight if it breaks out and then I am back to step 1.

        • You’re wise to go slowly, Sarah. Without seeing your apartment layout, it’s tough for me to comment on the situation in the dining room. Can you try distracting Isabel with a toy when she is in the dining room?

          • I have tried to distract her. She absolutely will not play at this time. Today I moved the baby gate so that they would eat closer to the dining area. I thought maybe I need to make some good associations there. Isabel was in the bedroom today. She couldn’t come to the baby gate. I finally moved her dish back about 8 feet and once Sadie ate, she ate (then vomited it up-she is clearly stressed by this). So I am going to work on these associations now. I did order spirit essences.

            I joke about this, but would taking them both to the vet (or even for a 2 hour drive in the car) then bringing them home together remind them of who each other is?

          • Taking them both out of your apartment could go either way, Sarah. It could increase stress levels and make things worse, or it could “hit a reset button.” I wish I had a better answer for you. Have you discussed any of this with your vet?

          • Thanks again for all your help. I wonder if it would hit a reset button or not, but I am not there yet. We have good intros and bad intros at this point. This morning, they spent 10 minutes in the bedroom together with no problem. They hung out with a baby gate between them for about 15 minutes this afternoon-till one made a leap and startled the other-then there was hissing and a bit of chasing, but nothing worse. So at this point, I will just take it slow and let it happen on the cats time.

            I want to thank you for taking all this time to answer my questions and give advice. It has been very beneficial and I have really needed the little pep talks.

          • Hi, It’s been a week and I thought I would update you. Its been 3 weeks since I took Sadie to the vet for vomiting and Isabel didn’t recognize her when she came back.

            I moved the feeding stations to an area that is more contested and things are going well. I had to start out with the cats about 8 feet apart and we are now about 2.5 feet apart. The morning introductions are the best. Isabel is usually able to walk by Sadie and explore but occasionally Sadie will hiss. For the most part, I think Isabel remembers Sadie-she actually gets excited when she hears Sadie in the morning- but Sadie seems to think Isabel is an intruder. How they can forget 5 years of living together, I don’t know.

            There is still a lot of tension from Sadie if there is no food for distraction.

            I have Spirit Essences Peacemaker supposedly arriving on Thursday -hoping the mail is on-time-as well as some Feliway spray to put on some specific areas.

          • I tried that when I first started intros and Sadie was distracted. It made Isabel uncomfortable and one of the two worst fights ensued-probably because I tried to remove Isabel rather than Sadie.

            And then I read that sometimes to early in the game can cause one cat to see the other as prey so I became weary of trying it again. Maybe now its time to do that.

            I think the most depressing thing is that every time I get hopeful, like when I wrote you yesterday, that things are actually moving well, we take 2 steps backward. There was a lot of hissing last night and Sadie vomited I think from stress-I had put a tall gate up so they could see each other without hurting each other. 30 minutes later things were steadily declining. So I separated them to other rooms.

            This morning that seems 80% forgotten, so by this afternoon I should be back where I was 1.5 days ago.

          • I wanted to say a final “Thank-you!” for all the advice and pep talks you gave. This week has signaled my cats getting along. We are about 90% of the way to where we were before this happened.

            I knew I was part of the problem, my stress level was so high, that it affected the cats. But I thought it was that one is particularly attached to me and saw the other cat as a danger to me plus a bit of jealousy.

            This week, one of them got out of the bedroom while I was gone-not sure how-and when I came home, there they were. There was some hissing, but mostly things were fine. And I found, if I stayed in the other room, they did better than if I was present.

            Each day has improved 10 fold from the previous.

            There were times this month when I was crying every night over this and just the fact that you “listened” made a difference, not to mention all the advice. So thank you!!!!!

            I give you a lot of the credit for getting my cats together again.

          • I’m so glad I was able to help, Sarah. And you bring up such an important point: the human’s energy is key in getting these situations to resolve, and yet, it’s incredibly hard to remain calm and not show your distress when you’re around the cats, when all you want is for things to return to normal.

  12. While we haven’t had this occur after a vet visit, we had one instance where a stray cat was outside our patio door window and one of our cats got so upset by the presence of the visiting cat, that she acted out and swiped at our older boy, slicing his cornea in the act. Poor thing didn’t even see it coming, he just sat there and took it. I separated them immediately, to assess damage and to give them both a time out to collect themselves. Wound up having to take him in for a check up – where he had it flushed and a round of antibiotic eye drops prescribed. All was well upon his return thankfully but, it taught us just a lesson in misdirected aggression for sure!

  13. Does Anyone Have this Issue Happen Without The Cats Leaving The House?
    I have had this occur before when one of the cats went to the vet, but lately this behavior will trigger in the aggressor cat with out leaving the house at all. It will last for over 24 hours and the aggressor cat will hide and seclude himself in the shower, under beds and will be aggressive to both me and other cat if communication is attempted. He will not eat, or drink during this time and toilet in his surrounding with out going to the litter box. It is like he is aggressive, but extremely fearful the entire time and this triggers without the cat ever leaving. It has happened 3 times over the last 2 months. I was starting to think it was a psychological cat bi-polar if that exists.

  14. We have 3 cats. The oldest cat, O’Leary would really like everyone except Mom to just leave, but most of the time he’ll put up with the others. Our other male, Gabriel and our female, Lily will sleep together and groom each other and it is usually Lily seeking out Gabriel. Gabriel has been on amitriptyline for years (well before Lily joined the household) due to aggression issues leading to idiopathic cystitis. Recently Gabriel become very ill and after exams, blood tests and x-rays, he was diagnosed with inflammatory bowel disease. Upon arriving home he and I were greeted by Lily with hissing, growling and swatting. I’m quite sure it was fear and smell based. She never was been good with any change in the house and acts out wheneever there are overnight guests or heaven forbid we go on vacation (helps if we are able to have her favorite sitter). I’m happy to report that not only has Gabriel responded very well to treatment, after a few days Lily returned to her loving self (until the next guest arrives).

  15. I have several problems. I don’t know what to do.
    My two cats Maya and Danny (mother and son) were very close before this incident, had never seen another cat outside of each other (other than my brother’s cat who passed away recently and Maya’s other kittens a few years short of a decade ago) now have to suddenly get used to not only a new environment but a new cat. My grandmother passed and left us her dog and cat. The dog should be no issue, as he has always loved cats. Casper the cat, however, did not take to Maya on their first meeting like he did with the outdoor female torti whom passed 2 years ago that occaisionally visited inside. I was hoping that since Casper liked the old torti and often looked out the door for her after her passing that he would be more open to a new girl. My mother’s logic was that once Casper liked Maya we could bring in Danny, and once he saw her be friendly with Danny he would see Danny was ok. It would be so much simpler if we weren’t in the process of moving things into my grandmother’s house and leaving ours to rent out to my cousin and his family. They will be moving in sometime in November. Both my cousin and his fiancée’s daughter are allergic to cats. While our dogs and my stepfather still reside nextdoor, my mother, stepsister and I mostly stay at grandmother’s. I was spending about two hours each day to spend with the cats nextdoor, more if the six dogs in the house didn’t set off my anxiety as well as the loud music my stepfather occasionally plays. Having Asperger’s makes dealing with certain noises hard, so I would just go up there to feed and spend some time with my cats and leave. I felt very bad for not being able to tolerate it for Danny, who is very attached to me and doesn’t like for me to be away. Before the moving issue, I stayed in my room the majority of the time. Even then he would cry if I was out too long. It only got worse after mostly moving nextdoor. The dogs express their ideas of me being gone too vocally and over affectionately for my liking, so I avoid them the most I can unless they are calm. Poor Danny starts crying the moment I get in the door and eats up the attention I give him. While I would have liked to take the cats to visits next door to get acclimated, both my mother and I prefer it be done while she is home, and she currently has a work schedule that makes it difficult. Maya and Casper have only met once. I figure all this is going to change soon. A few days ago I noticed an infected looking yet fresh scrape on Maya’s chin and went to check it out. Feeling of it, the area around it was hard and very unusual. Mom got her a vet appointment to which she went to the day before yesterday. Let me first say that I love our vet… but his gut feeling was that she very likely has a malignant bone growth and that the scrape was caused by her clawing at it. After he put her under to do a biopsy, he said he was a little more hopeful as there was a lot of pus which could mean its a bad infection. Bad, but treatable. But its still at the unknown phase. He gave her a shot of something I don’t remember to help the infection and said if she didn’t improve within a few days he’d send off the biopsy. He suggested we keep her in a secure room at our new home with wet food and drink so that we could keep a close eye on her. She did nothing but stay under the bed that night, sleeping off the anesthetic. Danny spent his first day without his mother, and was truly alone for the first time. So my mother said we might as well bring him down and move them in now instead of later. That’s where things went wrong. In my haste to not get clawed, I put Danny in the cat carrier before realizing grandmother’s poodle had peed all inside it. There was no way this cat was going anywhere without a bath, he was SOAKED. He did surprisingly well for his first bath. As my mother doesn’t have the appropriate shampoo, she used children’s gentle formula shampoo and body wash. While he nolonger has bad dandruff and smells fabulous… Maya doesn’t think so. He, however, doesn’t understand why his mother growls and hisses at him for merely looking at her. He currently doesn’t seem to care that she’s been anywhere. He acts towards her normally. We didn’t deal with her behaving like this when he got fixed years ago or his subsequent trip back after his tom-parts got an infection so I assume its because of his new smell. She tolerates his presence, I have seen him as close as two feet away but she cannot stand him to look at her. I know cats see eye contact as territorial, but Maya has always been one to lovingly stare at me or him for times it borderlines on creepy. Perhaps her having been anesthetized and possibly in pain added to her knowledge that there IS a strange cat in the house somewhere is causing it to be worse. I just wish I had known about the possibility of this sooner. If Maya didn’t have an issue that needed to be watched, this wouldn’t have happened. If grandma’s poodle had been fixed and properly house trained and didn’t have a fixation on peeing on things this wouldn’t have happened. If my mother had made the logical decision to put the cat carrier where he couldn’t get to it…

    I’m at a loss. I don’t want my previously happy cats who loved each other to be like this… I wish things weren’t so complicated… Any thoughts?

    • There are an awful lot of things going on that are causing stress for everyone, Lauren, and unfortunately, your mother’s advice of “you might as well move him in now instead of later” probably made things even worse. I would keep the two cats separated and start very slow, gradual introductions, as if they had never met. This can take weeks, or even months – the key is to go slow, and back up if things deteriorate. Here’s how to do it:

  16. What about flat out cat on cat aggression? My cat Lenore is a conundrum. She doesn’t care about the dogs in the slightest, but ever since I rescued her from the shelter ( at 12yrs old after being dumped by her other family) she hates, and I mean HATES my other two cats. She hisses, spits and swipes. I’m sure there have been scuffles when I’m at work. She has improved and now they can be in the same room at a safe distance and the only time they can be in paws length is while eating. I’ve used the challenge line method to accomplish this. I don’t need them to lump in a pile and groom each other, but I’d like to not have Mexican standoffs in hallways and kitchen doors. I refuse to give Lenore up and abandon her to a certain death.

    • It sounds like you probably need to work with a feline behaviorist, Heather. If the stand offs are in hallways and door ways, there may be things you can do to modify the environment, but it would take a good look at your living space to figure out exactly what is needed.

  17. The tactic I’ve found that has worked the best so far is to keep the carrier out at all times at home. This allows both cats to walk in and out and leave their scents. I also leave a towel in the carrier so that when I have to take one to the vet, the scents from home go with them. This calms the cat going to the vet and preserves some of their original scent.

  18. A friend of mine recommended I check out your page and the first thing I saw was this article and I feel like it was meant to be…

    We have a male cat, “Harold” who is approx. 11 yrs old and another, “Frosty” that is approx. 4 yrs old. They have never really gotten along (besides the occasional touching of noses and laying beside each other) BUT lately, the oldest cat is really not himself. He’s really aggressive AT HIMSELF, turning back to look towards his tail and hissing, growling like some sort of wild animal. My husband took him to the vet and he checked out fine, physically. He didn’t act that way at all while there. Right now he is sleeping sweetly beside me and I have woken up to him sleeping right beside me, almost hugging me and it was not like him (although it was really nice). He’s really sweet or really not- no in between. I also should add that recently my husband saved a kitten from being killed and she has NOT be in the house (except in our arms once and once when she ran in when I couldn’t stop her. They did not have contact) Could it really be because of her (she’s in our addition til she checks out OK at the vet and then we were going to bring her in – now I am not sure how to approach this whole situation) I have heard of plug in products or drops that help a cat destress BUT I don’t know where to begin. Sorry to go on and on…please help me with Harold. He’s been through so much with us. I just wish I could help him get back to himself (whacky, but not freaked out by himself and growling.hissing. Also, could it be his age and he’s “loosing his mind”- like people can get alzheimer’s?)

    Thanks in advance.

    • It’s possible that the new kitten is causing Harold’s behavior. Your questions are a bit too complex to answer in a simple comment. You may want to look through the Feline Behavior section on this site for articles on how to introduce cats to each other. Feliway Plugins can certainly help, as can holistic remedies. I would recommend Spirit Essences Stress Stopper to start with. If you’d like more detailed advice, I’d be happy to schedule a phone consult with you.

  19. My 13 year old cat has stage IV kidney failure and has been to the vet a number of times in the last six months. He’s a Persian with very woolly fur, so, like we’ve done many times in the past, we had him shaved so he’s able to groom better and be more comfortable, especially in the recent very hot weather. He’s never been received back at home poorly by the other resident kitties until this time. My assumption is that shaving him not only revealed a new scent, the shampoo, but also the scent of his body chemistry which is definitely going to be change week to week as his kidney failure progresses. We think that by taking away his fur that likely captured all of the familiar scents of our home, we’ve left him smelling like a stranger, and one of our kitties has taken to stalking him, attacking him, and peeing on things he sleeps on. It’s gotten better over the last two weeks because I separate them when they’re unsupervised (the attacker would literally wait for us to leave the room and then pounce), feed them with more distance between their plates, and put away the beds/blankets the sick kitty uses when we’re not around. While we aren’t having attacks, per se, for the last few days, we are still getting some marking, and we have a sick, jumpy kitty along with an agitated, on-edge healthy kitty. Our third resident kitty has been staying more out of sight as not to get in the middle of things, I think. But, she’s been seen hissing at the sick kitty as well. Though, she’s not attacking–just staying away. It’s frustrating to have things being pee marked, like our bed, but it’s more disheartening to me that my sick old guy has lost his BFF because of a miscalculation on my parts by having him groomed without realizing what the outcome could be.

    • I’m so sorry this is happening in your household, Kristine. If you’re open to using holistic remedies, I’d recommend trying Spirit Essences Stress Stopper, Peacemaker and Safe Space for Cats, in addition to what you’re already doing. If you decide to order, you can get a 10% discount by using code CONSCIOUSCAT.

  20. I have two cats daughter and mother. To take both cats to vet in the same time helps. I know it from my own experience. Took Shiva and Buttons not just for checkups but for fixing them. I had no problems with aggression at all.

  21. This has happened to us, but not because of a vet visit. It happens when our indoor cats encounter a neighborhood outdoor cat through the window. KitKat “forgets” who Snickers is, and she hisses and fights with her for up to a week after seeing that outdoor cat. I think ususally Snickers startles KitKat by accident when she is in the throes of seeing that other cat, and that is the catalyst for the first fight. At least that’s what we’ve seen when we’ve been home. The very first time this happened, we were not home. We came home to unexplained hissing and puffy tails. KitKat often pees herself suddenly that first time too. (Thankfully they both love water, so baths aren’t a problem!)

    They were littermates and are now 3 years old and have spent their entire lives together. It’s very upsetting to us, because we can’t figure out how to keep that outdoor cat out of our yard. We don’t know who it belongs to, but it is plump so it doesn’t appear to be a stray. If you have any advice about something we could do to keep the other cat out of our yard, I would appreciate it!

    • That form of aggression is actually called redirected aggression, Kim, and it is very upsetting when it happens. There are motion activated devices that can keep stray cats out of your yard without harming them. Alternately, you may need to block the windows so your cats can’t see the outdoor cats.

      • Ah, redirected aggression. Makes sense. What do the motion activated devices actually do? Is it a sound? Will it negatively affect our cats inside? While it is very upsetting to us, it is also very interesting to watch it from a more objective standpoint. It is truly amazing to me that she can “forget” her sister like that. And it’s just as amazing that it’s temporary. I hope it is always temporary. It’s tough to live with for the first day or two days. Then as it gets better, it becomes less intense and almost raw instinct. “I feel like I have to hiss at you but I don’t really know why and I’m not still mad at you, but I think I might be…” Thanks!

        • The devices emit a high-pitched sound that the human ear can’t hear. Here’s an example of one:

          It’s good that it’s only temporary with your two, but the more frequently it happens, the better the chance that this becomes habituated behavior between them. It would be best if you could eliminate the trigger.

  22. I had this issue with my sweeties. A brother and sister. It was traumatizing to me too. Now I take them both to the vet together and I no longer have this problem at all.

  23. When this happened with my cats I put a bit of vanilla flavoring on each cat’s forehead and butt. I had read that once they smelled alike they would be okay, and it worked every time.

    • That sounds like an excellent idea Debi!! I have nothing to lose by trying it. Thank you so much 🙂

    • I had heard about this tip before, but never heard from anyone who used it that it actually worked. Thanks for sharing your experience, Debi! Betty, will you let us know whether it works for you?

  24. I had my fingers crossed when I came to read the whole article that I may have finally found the solution to one of my cats (the tortie) that suddenly started not getting along with my cat Rocky. My four cats have been together for over 9 years and about a year ago or so suddenly Columbia started to go after Rocky for no apparent reason. Columbia has been to the vet but not Rocky (he had the home visit vet). Columbia only has curiosity Janet and Brad come home from the vet, no real aggression.

    She would stalk him, chase him, try to corner him, etc. and it hasn’t stopped. All that has happened out of the whole thing is that Rocky has claimed the kitchen and one of the bathrooms as his turf and will occasionally go after Columbia and Columbia (being a true tortie) has claimed the rest of the house and will go after Rocky, depending on her mood.

    I tried one of the essences however it seemed to do no good. I just want to restore peace in my house and get rid of this aggression.

    • Territorial aggression can be challenging to manage, Betty – I’m sorry you’re dealing with this. Do you have plenty of vertical space (cat trees or shelves) so they can both get away from each other?

      The essences will need to be used in conjunction with behavioral modification. I’d recommend Peacemaker and Stress Stopper for both of them, and Safe Space for Cats to spray in the areas they consider their territories.

      • I think it is the Peacemaker that I already went through a bottle of and it had no effect on either kitty 🙁 I can only afford to buy and try one more right now, which do you recommend?

        As far as space, yes they have a floor to ceiling cat tree. Fortunately I haven’t seen or smelled any instances of spraying by either one..knocking wood!

        • Betty, has Rocky had his anal glands expressed? It sounds a bit daft, but if a cat has impacted anal glands, other cats may act aggressively toward the cat with the problem. Cats’ sense of smell is so acute that although we can’t smell it, the festering fluid in the impacted gland is extremely of-putting to other cats. Please have Rocky examined and his anal glands expressed if you can – it won’t hurt and might help! Best of luck!

          • I’ve heard this theory about anal glands causing aggression in cats a few times now, and having them expressed seems to resolve the issue in some situations. As for “it won’t hurt” – I think the cat might disagree :-)!

    • your case sounds like from the annals of My Cat from Hell. You can contact Jackson Galaxy on his website for advice. I feel for you. I’ve seen cases such as yours successfully treated by Jackson.

      • I’m using his techniques from his book Cat Daddy. I’m a huge fan of the show too. That’s how I keep the damage down with redirecting and challenge lines. We live in a small apt and I’d love to work on escape routes regarding the standoffs in hallways and doorways but its not feel able at the moment. My boyfriend is at his wits end bc he doesn’t want three cats and three dogs anyway. His “rule” is four. But being a vet tech I tend to just end up with them. Lenore was gong to be euthanized by our humane society based on the fact she was “old and fat” there fore not adoptable. I refuse to give her up but I feel where my boyfriend comes from when he sees me scratched or bit by her. The latest was a lung to the face. I wonder if Jackson would come to Idaho?

  25. I always bring both cats to the vet, for exactly this reason. It may not help if one cat is very sick (when my Bear was sick with FIP, my other cat was very hostile towards him no matter what I did), but for routine vet visits, it works like a charm.

  26. This is really interesting and I didn’t realize how difficult it can be to resolve these types of problems. So far, the animosity between Katie & Waffles is no different when one of them has been to the Vet. Since they are still learning to live peacefully together and aren’t exactly each other’s BFF yet (or ever!) my Vet recommended not bringing them in together. Because Katie is still anxious around Waffles, she feels it would cause more stress. That may change in the future, so we’ll see.

    I’m a believer in Stress Stopper now, thanks to you! It’s hard to believe something so simple and so easy to use can be so effective. Wow!

    : ) Glogirly

    • I have wondered about whether taking both cats to the vet’s would cause additional stress, and it sounds like your vet agrees, Debbie.

      I’m so glad the Stress Stopper is working for you!

  27. I have this problem with my cats Ernie and Wally. Whenever Ernie came home from the vet, Wally would hiss, growl and swat at him. The first time this happened, it lasted for nearly 2 weeks. Nothing I tried seemed to help…rubbing each cat with a towel to make them smell the same. I just ran interference to make sure the problem never escalated. Eventually Wally calmed down. BTW, this never happened the other way around, when I brought Wally home from the vet, Ernie never reacted negatively towards him.

    I mentioned the problem to my vet and she told me that when I brought Ernie in I should also bring Wally. That’s what I started doing, which isn’t the most convenient thing to do, but it really helped. While there, I always have my vet rub Wally and she even puts a little alcohol on him so the smells will be the same on both cats. Wally still will hiss a little when we get home, but after an hour or so, things are pretty much back to normal.

    Island Cats’ mom Sue

  28. Now that explains it! Last year, Charlie briefly escaped one evening and had an adventure which kept him busy until midnight when he started throwing himself at the front door. I let him in ad comforted him since he seemed confused but Chelsie, his big sister hissed at him and backed away from him. She refused to go near him for a day or so but luckily no one showed any aggression. I wiped him down with cat wipes which she likes too so they got over it very quickly. I’m so lucky.

    • I just remembered something that happened a couple of years ago when Chelsea got out and the neighbor’s cat walked her home in 20 minutes or so. At that time Charlie had no problem with her. Isn’t it remarkable how different their personalities are?


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