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Is my cat's sudden side hair loss from a vet visit or vaccine shot?

Updated On September 23rd, 2025

Pet's info: Cat | Russian Blue | Male | neutered | 15.8 lbs

My cat is having sudden hair loss on his side this started to happen the day after his visit to the vet. First day found some hair on the floor. Couldn’t find where it came from. Today is day 3 and the spot is about 2” in size. It seems to be progressive. No dry scaling a couple of scratches. He did receive a leukaemia shot. But otherwise is good health

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1 Answer

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Answered By Christie Long, DVM

Veterinarian, Certified Veterinary Acupuncturist

Published on May 20th, 2018

If this hair loss is in the area where the vaccine was given (sorry, I can't tell from the pictures exactly where it is) it could be a reaction to the vaccination. I'd recommend placing a call to the vet and describing the location of the hair loss; this may be an aberrant response to the vaccine that needs to be reported to the manufacturer.

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