You are here:

Ask the Veterinarian/Cat allergic reaction to yearly shots


Hello doctor,

Tonight my cat was scheduled for his yearly dose of rabies and his fvrcp shot (every 3 years). Everything went fine but once I got home my cat instantly started aggressively licking his entire body, to a point where he was biting his paws and it looked like he was attacking himself. He was very distraught and frantic and was running around and hiding anywhere where I couldn't reach him. It looked like he was having twitches. So I took him back to the vet, she gave him a Benadryl shot and was reluctant on giving him a cortisone shot but I told her not to after reading the potential effects online on my phone. Unfortunately, halfway home, my cat started violently licking himself again in his carrier, so I turned right back and they gave him the cortisone shot and told me to observe him for the next half hour to see if it stops and if not to take him to the emergency vet. Fortunately the reaction stopped, but now I'm so worried of all the side effects of the cortisone. My cat is somewhat lethargic but now he suddenly got up and is wandering around as usual, but his hunger levels are extreme. He's eating so much and the first time he went to eat he ate so quickly he threw up along with a massive hairball (I assume that's from the licking), and right after he has went to eat again twice. And I've read online that cortisone has changed the behaviour of some people's cats- as in they become lethargic and just eat and sleep and lose all their character. I'm worried that this might happen to my cat. Also, my cat is already prone to UTI's and is also a bit overweight, so I don't need these to get worse, as it is stated that cortisone does. Any input would be greatly appreciated.

Thank you!

hello john,
In this case cortisone has been used as life saving drug to counter the anaphylactic  reaction caused due to the vaccination.Some animals very rarely have this,may be due to some constituents in the vaccine.This reaction can sometimes be controlled by way of antihistamines [found in benadryl] if it is mild,but severe  reactions can lead to shock and eventually death which has to be countered by cortisone.
You didn't mention the age of your cat,and it may be the age of your cat and type of food or the feeding habits which may have a say in the  present status.Side effects to cortisone can  be attributed to regular use and not for a single use either.
So on a whole you may consider a thorough examination of your cat including hormonal imbalances so as to rule out conditions like diabetes.



Ask the Veterinarian

All Answers

Answers by Expert:

Ask Experts


Dr S Bindu Anand


Large and Small Animal Medicine and Surgery, Farm Management,Preventive medicine


A Senior Veterinary Surgeon with more than 25 years’ experience in the field of Veterinary Science and Animal Husbandry. Mixed animal Practice that will utilize my skills in medicine and surgery, public health, client relations, and developing relationships within the community, such as humane society

Veterinary Consultant with Department of Animal Resources,Ministry of Environment,State of Qatar (Present). Animal Husbandry Department, Government of Kerala, India. Oakland's Park, Gloucestershire, United Kingdom. Severnside Veterinary Center, Gloucestershire, United Kingdom. Saud Bahwan Group, Sultanate of Oman. Trivandrum Regional Co-operative Milk Producers Union,Kerala,India.

BVSc & AH (Bachelor of Veterinary Science and Animal Husbandry) 1990. College of Veterinary & Animal Sciences, Mannuthy, Thrissur, Kerala, India under Kerala Agricultural University. Certificates Of Accomplishments- Equine Nutrition- University of Edinburgh Principles of Public Health-University of California, Irvine. AIDS- Emory University, Atlanta, Georgia. General Environmental Health – EPHOC-Tulane University School of Public Health and Tropical Medicine and the University of Alabama at Birmingham School of Public Health. Food Protection-EPHOC-Tulane University School of Public Health and Tropical Medicine and the University of Alabama at Birmingham School of Public Health. Zoonoses:University of Minnesota-School of Public Health online. Food Safety:University of Minnesota-School of Public Health online. Occupational Safety and Health-EPHOC-Tulane University School of Public Health and Tropical Medicine and the University of Alabama at Birmingham School of Public Health. Rabies Educator Certified -Global Alliance for Rabies Control. Animal Handler & Vaccinator Educator Certified -Global Alliance for Rabies Control. Wildlife Conservation-United for Wildlife

©2016 All rights reserved.