Hi Amy,

Thanks for your question.

Benadryl contains the antihistamine, diphenhydramine, and generally speaking, Benadryl is safe but there are conditions where it might be dangerous to give this medication to your dog and that includes dogs with glaucoma, urinary problems, vomiting, heart disease, high blood pressure, and also hyperthyroidism, which is very uncommon in dogs but if it’s present, we need to be very careful in using Benadryl.

An important point to make is that whenever we’re giving anything to our dogs or our cats, you really need to be talking to your vet because they will be able to give you specific advice for your pet. Any information that you read online or I’m giving here is going to be just general advice for the majority of the population and it’s never going to be individual advice for a specific patient.

If we think of Benadryl or diphenhydramine as a whole, it’s often given more often than not to treat allergic disease in dogs. When it comes to giving antihistamines it seems that dogs do have a very individual response. Some respond to one and not another and you may need to cycle through several different types of antihistamines before finding one that works for your dog.

One of the potential side effects of Benadryl in dogs is sedation and it’s primarily this sedative effect which people rely on when it comes to treating anxiety although the drug does have some kind of anti-anxiety effect as well that’s separate from the sedation. The other thing to think about is if we’re using it on a regular basis, then actually the sedative effect generally wears off and some dogs may be unaffected to start with. While it can be used for some cases of anxiety, it might not be beneficial if you’re using it regularly or if your dog is one of that doesn’t respond. While Benadryl can be used to treat anxiety, it’s probably best suited for really mild anxiety and used in conjunction with other management techniques.

As always please consult your veterinarian.

I hope this helps.

Dr. Alex Avery