Cat has lump after vaccine. Is it a reaction? When to see a vet?

Normally, there will be a small bump where a vaccination is given and this can persist for several weeks to months. If it persists for longer than 3 months and / or continues to grow in size, I would recommend having a veterinarian examine Simba so that the most appropriate diagnostic and treatment recommendation can be made. Sometimes, vaccines can cause cancerous tumors to grow in the area where the vaccine was administered. This is less common now, but still a risk. I hope this helps! Please let me know if you have any further questions / concerns and I would be more than happy to help you further.

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.

That is a very common occurrence after vaccination. The vaccine can cause a localized reaction and it should resolve on its own within a month. If it persists, seems larger, or bothers him that have your vet take a look at it.

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!

It does not look like post-injection reaction. I would rather suspect an insect bite, reaction to a tick, cat bite (if Ori goes out at all) or self-inflicted small wound from scratching the area. Please, keep an eye on it, small skin wounds often heal rapidly without treatment. If there is any discharge from the wound you can use 4% chlorhexidine skin solution to clean it. If it gets bigger or starts bothering Ori, take her to your local vets for a check.

I hate to hear that Tigresa is giving you a scare! In general, vaccines don't go in the area by your thumb. I would recommend to take her to the vet to have the mass aspirated. This should give you an idea if this is a sarcoma or another type of a skin mass. If could be any of the things you listed above. Typically aspirates do not require sedation or stitches. Best of luck with your sweet girl.