Medically reviewed by Daniel Combs, MD Benadryl (diphenhydramine) is an over-the-counter (OTC) antihistamine commonly used to treat allergies that is also sometimes used as a sleep aid for insomnia.

Signs of a Benadryl allergy include: Red rashes on the skin Swelling of the face and tongue Runny nose and eyes Diarrhea, vomiting, and upset stomach Skin chewing or licking Symptoms of a Benadryl ...