Benadryl Can Be Used to Treat Allergies in Dogs

Benadryl (Diphenhydramine HCl) is a great drug for people with severe allergies, but it also works well for dogs that have severe allergic reactions.   Common symptoms of an allergic reaction are urticaria (hives) and angioedema (swelling of the face).   Urticaria and angioedema  usually develop within 20 minutes of being exposed to the allergen (the thing that the animal is allergic to).  These can be caused by hypersensitivity (or allergic) reactions to chemicals, something eaten, drugs, or even sunlight.  Hives and swelling of the face are not typically life threatening and can be managed with an antihistamine, like Benadryl.  Symptoms involving the the respiratory system (the dog is having trouble breathing) are far more serious and require immediate medical attention.  The following table is the recommended dosing of Benadryl for dogs:

A dog can have 1 mg/ pound of body weight twice per day.  Benadryl tablets contain 25mg of Diphenhydramine HCl.

Dog’s weight in pounds	Concentration of Benadryl  to administer (mg)
12 pounds	12 mg (1/2 tablet)
25 pounds	25 mg (1 tablet)
50 pounds	50 mg (2 tablets)

Children’s Benadryl is often easier to give to a dog, as it is flavored, and chewable.  Often the dog will just eat a flavored tablet.  Benadryl can also be placed into the back of the dogs mouth, and the throat can be gently rubbed to get the dog to swallow.

Anaphylaxis is a rare, life-threatening, immediate violent allergic response to something injected or ingested.  If the animal is left untreated, it will result in shock, cardiac and respiratory failure, and death.  Compounds that can cause anaphalaxis are antibiotics, some medications, stinging insects, vaccines, and food for animals that are susceptible.  The symptoms of anaphylaxis are:  shock, sudden onset of diarrhea, vomiting, seizure, coma, and  even death.  The animal’s limbs will feel cold, and it will have very pale gums.  The pulse is generally weak, even though the heart rate is very fast.  There is no facial swelling in anaphylaxis.  If your pet has symptoms of anaphylaxis, emergency veterinary care is needed immediately (like within a few minutes), or it is likely that the animal will die.

If your dog has a history of severe allergic reactions, ask your vet about an epi-pen, a single dose syringe filled with epinephrine, that can be transported with the animal on outings, and administered in an emergency.  This will buy you more time to get to the veterinarian before the allergic reaction or anaphylaxis becomes life threatening.