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Will Benadryl make my dog drowsy? Do dogs build up a tolerance?

Updated on September 23rd, 2025

Pet's info: Dog | Mixed Breed | Female | 5 years and 8 months old | 11 lbs

Does Benadryl cause drowsiness in dogs? Also if used daily do they tend to build up a tolerance so it doesn’t work as well long term if used daily?

2 Answers

Most Helpful Answer

Answered By Catherine Stecyk

Veterinarian

Published on May 12th, 2019

Hello and thank you for reaching out to Petco Pet Education Center, formerly Petcoach. Benadryl can definitely cause drowsiness in some dogs, but this tends to be dose-dependent, meaning the higher the dose, the more likely a dog is to become drowsy. Some dogs are not very affected, though. We do not typically see a tolerance built up. The dose range is pretty wide, though, and Benadryl can be safely given up to 4 times per day. Depending on the reason that Kiwi is taking the Benadryl, I recommend consulting with your vet to see what dose & frequency they recommend. I hope this is helpful!

1Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Anna M., DVM
Veterinarian
Published on April 16th, 2019
Hello, and thanks for your question about Kiwi. I'm interpreting that your vet recommended the benadryl for Kiwi's allergies, since benadryl won't help with anxiety. Benadryl doesn't necessarily always cause drowsiness in dogs - and the dose will factor in. I recommend trying Benadryl if that was your vet's advice, and see if it does cause Kiwi to be sleepy. It might not! If you don't like how she responds to the benadryl, then there are other (and more effective) allergy medications available that you can discuss with your vet, such as cytopoint injections or apoquel pills. There are also other medications or supplements that can be discussed for anxiety if indicated. But I'd start with the Benadryl dose your vet recommended and go from there - you can call them with an update and ask about alternative medications if need be!

Hope this helps! :-)
1Pet Parents found this answer helpful

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