Diphenhydramine hydrochloride is a type of generic medication available in both prescription and over-the-counter medications. Despite its effectiveness at relieving allergy symptoms and treating insomnia, diphenhydramine poses a risk for side effects in some patients.

Types of Side Effects

The most common side effects of diphenhydramine are drowsiness, dizziness, lack of coordination, stomach discomfort and thickening of mucus in your airways.

Special Populations

Diphenhydramine is not safe for use in infants, pregnant women or nursing mothers, reports the U.S. National Library of Medicine. Rather than experiencing drowsiness from diphenhydramine, many children become excited or restless from the drug, while the common side effects of the drug are more likely in people over the age of 65.

Drug Interactions

Taking diphenhydramine with alcohol, sedatives or tranquilizers may cause excessive sedation, reports the U.S. National Library of Medicine. Taking monoamine oxidase inhibitor antidepressants (MAOIs) has the potential to cause dryness in your eyes, mouth or sinuses.

Risks

Some patients develop severe allergic skin reactions from diphenhydramine, which may lead to anaphylactic shock or even death. Other risks associated with diphenhydramine include low blood pressure, shortages of blood platelets or white blood cells, anemia, changes in heart rate and seizures, warns the U.S. National Library of Medicine.

Considerations

If you have a history of glaucoma, heart disease or prostate enlargement, it may not be safe for you to take diphenhydramine, reports the Mayo Clinic. Because it is known to cause drowsiness and dizziness, avoid driving or operating heavy machinery until you know how diphenhydramine affects you.

Source:

U.S. National Library of Medicine Daily Med: diphenhydramine hydrochloride (Diphenhydramine Hydrochloride) capsule

Mayo Clinic: OTC sleep aids and supplements