BENADRYL Allergy Liquid provides fast, effective relief of allergy symptoms. This liquid has a great-tasting cinnamon flavour to make it more pleasant to take your medicine. Each teaspoonful (5 mL) contains 12.5 milligrams of the antihistamine diphenhydramine hydrochloride to treat sneezing, runny nose, itchy and watery eyes, and hives. BENADRYL  Allergy Liquid comes in a 100-millilitre bottle.