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My 27lb dog has heartworms and vaccine itch. Can I give him Benadryl?

Updated on September 23rd, 2025

Pet's info: Dog | Mixed Breed Medium (23 - 60lb) | Male | neutered | 2 years old | 30 lbs

Is Benadryl ok to give a dog with heartworms who has NOT yet started his treatment? He has been a bit itchy since getting a vaccine a day and half ago. But he is energetic , eating normal, etc. vet was not concerned but I think he needs some relief! He is 27 lbs, is 1 tablet the recommended dose? Thanks!!

1 Answer

Most Helpful Answer

Christie Long, DVM

Answered By Christie Long, DVM

Veterinarian, Certified Veterinary Acupuncturist

Published on December 24th, 2016

Benadryl (diphenhydramine) is often given as a pre-treatment prior to giving treatment for heartworm disease to prevent a reaction, so there aren't any specific counterindications to using it in a dog with heartworm disease. However, if your dog is still itchy 24 hours after getting a vaccine, I would fear a worsening reaction, and I would recommend taking him in for a dose of a stronger medication - a steroid - which will definitively work and stop any reaction, as well as the itchiness. I find that Benadryl (used orally) is rarely very effective at stopping itchiness in dogs.
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