Diphenhydramine Side Effects

Possible side effects of diphenhydramine are listed below. Call your doctor or pharmacist for medical advice about side effects if they are severe or do not go away in a few days.

• Drowsiness
• Dizziness
• Dry mouth
• Nausea
• Vomiting
• Constipation
• Loss of appetite
• Chest congestion
• Headache
• Muscle weakness
• Nervousness
• Hyperactivity or increased excitement (in children)

Rarely, diphenhydramine can cause more serious undesirable effects. Call your doctor immediately or seek emergency medical help if you experience the following signs and symptoms after taking diphenhydramine:

• Vision problems
• Pain with urination or trouble urinating

The above list may not include all the potential side effects of diphenhydramine. Tell your doctor if you have any unusual side effects or if they do not get better over time. You can also report unusual side effects to the Food and Drug Administration at 1-800-FDA-1088.

Diphenhydramine Overdose: In case of a known or suspected overdose of diphenhydramine, call the local poison control center or provincial poison control center right away. You can also call the national poison control center at 1-800-222-1222. If a person has collapsed, cannot breathe, or has had a seizure, call 911 for emergency medical help.

Source: FDA