Why does my cat have a bump where he got vaccinated a week ago?

It does need to be noted with your vet to verify if it is a vaccine reaction. Cats can have injection induced sarcomas which are cancer and require surgery. The general rule is if it is there longer than 3 months or gets larger, then surgery is warranted, otherwise they go away on their own I would have them document the vaccine site and the size for proper monitoring in the future.

Great question! This lump could be a localized reaction to the vaccine if the lump is in the area where the vaccine was given. Other options could be a cyst or a benign tumor. Given it's not painful and if she is otherwise acting normally, this isn't an emergency. Keep an eye on this lump, and if it doesn't go down over the next couple of days or gets bigger, then I would have Poppy seen by a vet. Good luck, I hope this helps!

Poor girl. Due to her age a mass here would be less likely as the cause for this hard lump. This may be an abscess or even a cyst. It is difficult to tell without feeling it in person, however, if it does not go down on its own within a few days to a week, then I would recommend having your vet check it out further. If it is an abscess, then cats typically will start to act ill (decreased appetite, low grade fever, lethargy) after a few days, in which case the abscess would need to be drained by your vet and then KitKat would need a short course of antibiotics to get things to heal well. Otherwise, I would recommend monitoring this for now to see what happens. I hope that Kit Kat's strange lump heals well soon! : ) Best wishes and take care.

Hello and welcome to Petco Pet Education Center, formerly Petcoach. Soft masses that are part of the skin can be either abscesses (pockets of infection), small bits of swelling from vaccine injections (these can last a few months sometimes), fatty masses, and less commonly in a 4 month old kitten, cancers. I would monitor it, if Bean is painful or if it is growing or changing get it looked at right away, otherwise just monitor for now and have it assessed by your vet next time you are in. Best of luck with Bean!

Well bumblebee is quite the handsome cat. A bump like that could be a local reaction to a vaccine if he has recently had any shots, caused by a bug bite or bite wound from another animal, or even a benign or cancerous tumor. Since it is a new growth, I would have your vet take a look at it. Your vet will be able to aspirate it and determine if it needs to be watch or surgically removed or if he just needs some antibiotics. I do not think he will die from this, but early intervention is key. I hope this helps.

The most common lumps on cats are pockets of infection, or an abscess from a cat fight. An abscess is generally hot to the touch and painful and may cause a fever and lethargy. It also could be a tumor which often are non painful but can be malignant and will grow if not removed. Also some cats get a skin reaction to a vaccination if it’s given in that location and the swelling should improve over a week or so. I recommend a veterinary exam so they can feel the lump, take her temperature and decide if further treatment is needed. Thanks for using Petco Pet Education Center, formerly Petcoach to help you care for your cat.

Thank you for using Petco Pet Education Center, formerly Petcoach! It is difficult to see a lump in the photo, but at Capernicus’s age, malignant growths are fairly unlikely. This may be a reaction to a vaccine if administered recently that should disappear with time. I recommend keeping an eye on it and having the spot seen by a vet if there is any discharge, bleeding, increase in size, or it seems to be bothering him. I hope this helps and that all is well!