Which antihistamines are safe for dogs?

According to the American Kennel Club (AKC), you can give the antihistamine Benadryl (diphenhydramine) to your dog, but you should always check with your vet first. Although the U.S. Food and Drug Administration has not approved Benadryl for dogs, it is safe in the appropriate dose, and it is commonly used by vets to treat skin allergies that cause itching and scratching.

Benadryl can be used to treat dogs with:

• Hives
• Swelling
• Cough
• Sneezing
• Runny eyes or nose

Because Benadryl has a side effect of drowsiness, it may also be given to calm an anxious dog or to prevent motion sickness if your dog needs to travel. Your vet may tell you to avoid Benadryl if your dog has certain medical conditions or your dog is or may be pregnant. Your vet may also want to see your dog to find out what is causing your dog’s symptoms.

Benadryl can be dangerous for your dog if you give too much. An overdose of Benadryl can cause seizures and other side effects. The safest way to give Benadryl is to give it according to the weight of your dog. AKC says the dose for Benadryl is 2 to 4 milligrams per kilogram of body weight, two to three times per day.

Do not use a time-release capsule form of Benadryl because it can deliver too much Benadryl to your dog.

Other antihistamines safe for dogs

Other antihistamines can also be given to dogs, based on their weight. These include the below antihistamines:

• Cetirizine
  1 milligram per kilogram of body weight or 10 to 20 milligrams per dog, once or twice per day
• Clemastine
  0.1 milligrams per kilogram of body weight, two times per day
• Chlorpheniramine
  Dogs under 20 kilograms
  4 milligrams, three times per day
  Dogs over 20 kilograms
  8 milligrams, three times per day
  0.25 to 0.5 milligrams per kilogram of body weight, three times per day
• Cyproheptadine
  0.25 to 0.5 milligrams per kilogram of body weight, three times per day
  1.1 milligrams per kilogram of body weight, two times per day
• Fexofenadine
  2 to 5 milligrams per kilogram of body weight, once or twice per day
• Hydroxyzine
  0.5 to 2 milligrams per kilogram of body weight, three to four times per day
• Terfenadine
  5 milligrams per kilogram of body weight, two times per day
• Trimeprazine
  1 milligram per kilogram of body weight, two times per day

The safest dose is different for different antihistamines, so always check with your vet first.