Diphenhydramine hydrochloride is the active ingredient (the component with the medicinal property) in Benadryl. In addition to the active ingredient, there may also be fillers or other ingredients in the medication. These are the inactive ingredients. The inactive ingredients may vary, depending on the particular Benadryl product. For a complete list of inactive ingredients in Benadryl, refer to the label of your particular product.
What Are the Ingredients in Benadryl?
Benadryl® (diphenhydramine hydrochloride) is an antihistamine used for several different purposes. As with all medications, Benadryl contains an active ingredient plus several different inactive ingredients.
Active Benadryl Ingredients
The active ingredient (the ingredient with the medicinal property) of Benadryl is diphenhydramine hydrochloride. Diphenhydramine is part of a class of drugs called antihistamines. Specifically, it is an H1 receptor antagonist. This means that it blocks a specific type of histamine receptor in the body (known as H1 receptors). Since allergic reactions are partly caused by the release of histamine from certain cells in the body, diphenhydramine can help relieve or prevent allergy symptoms.
Diphenhydramine also blocks acetylcholine receptors, an action which produces some of the bothersome side effects of the medication (such as dry mouth or difficulty urinating) but also makes the drug useful for some uses (such as for Parkinson's disease or for relieving a runny nose due to the common cold).
Like many antihistamines, diphenhydramine also works as a sedative. This action has made the medication useful as a sleep aid but also limits the usefulness of the medication for other uses (since drowsiness can be a bothersome side effect).