The human allergy medication diphenhydramine hydrochloride (HCL) can be used to relieve certain allergy symptoms in dogs, notes Trupanion. Also known by the trademark name Benadryl, this medication can be prescribed by veterinarians to treat other health concerns like reactions to insect bites, motion sickness and muscle tremors. Diphenhydramine HCL should only be used under the supervision of a veterinarian, and only pure diphenhydramine HCL is safe for canine consumption.
Diphenhydramine HCL can be a great medication to use in certain types of emergencies, according to About.com. Allergic reactions from insect stings can be lessened if diphenhydramine HCL is administered quickly. These stings can become life-threatening depending on their location. The appropriate dosage varies depending on the dog's age, size and overall health, so the appropriate use of this medication in emergency settings should be discussed with a veterinarian.
PetMD notes that diphenhydramine HCL can cause drowsiness, dry mouth, vomiting, diarrhea, loss of appetite and reduced urination. A veterinarian should be consulted if these side effects occur.
For dogs with high blood pressure, glaucoma, asthma, prostate disease, heart disease or certain other conditions, diphenhydramine HCL may not be appropriate, notes Vetstreet. Even if the medication is deemed necessary, a veterinarian must carefully monitor the dosage.
According to petMD, diphenhydramine HCL is an antihistamine that works by blocking histamines that cause swelling, itchiness and inflammation. It also prevents a dog's airways from contracting due to an allergic reaction.