Hard Lump in a Kitten's Right Leg From a Rabies Shot

Rabies vaccines are required throughout most of the United States.
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Rabies vaccines save lives, but that doesn't mean they are risk-free. There's a good chance your furry friend will develop a small bump or swelling near where he got his shot. Cats normally receive rabies vaccines in their right rear leg and a multipurpose shot on their front right shoulder.

Local Swelling

Vaccines aren't easy on your kitten's immune system. Their purpose is to challenge your pet's body into producing antibodies against future infection. Since pathogens are being injected during a vaccination, your kitty probably won't feel too great for the next few days. A small, hard swelling may appear where your kitty got his shot, but these nodules are painless and go away after a few weeks, according to Cornell University College of Veterinary Medicine. Other mild reactions include a slight fever, lack of appetite and sneezing for up to a week after the vaccination.

Allergic Reaction

Severe allergic reactions to a rabies vaccine are rare, but they can be pretty rough for your cat. Symptoms develop within a few hours, so you may notice something is wrong before you even get home from the vet. The area around the injection site may swell up during an allergic reaction. Your cat may be a little nauseous and his face may puff up a bit too, according to University of Illinois College of Veterinary Medicine. Contact your vet immediately if you notice any of these symptoms.


You won't see a sarcoma right away. In fact, you may not even remember that your kitty had a shot where this new lump appeared. Sarcomas are tumors that develop directly under your kitty's skin and slowly expand. Sarcomas can appear weeks or months after the injection. While any vaccine can create a sarcoma, these unnatural growths are associated with the rabies and feline leukemia vaccines, according to University of Illinois College of Veterinary Medicine. They grow slowly to at least half an inch in diameter and persist indefinitely.

Diagnosis and Treatment

Taking your kitty to the vet in the event of a lump is always a safe bet. It will make you feel better to learn that it is just a harmless swelling, if that's the case. Treatment is only required in cases of allergic reactions or sarcoma. In the case of allergies, your vet will give your kitty something to stop the inflammation caused by his immune system. Smaller sarcomas can be surgically removed before there's a risk of the cancer spreading to other parts of your cat's body, but large ones may require amputation of the leg to stop the dangerous growth from spreading.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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