Research In Action

On just one single evening in July, the staff at The Poison Control Center at CHOP found themselves helping regional hospitals with five distinct cases involving teenagers with diphenhydramine “overdose.” This night was in line with our Poison Center’s observation noting an increasing number of diphenhydramine cases at three regional children’s hospitals, shared at meetings of the Pennsylvania Chapter of the American College of Emergency Physicians and at the North American Congress of Clinical Toxicology. Annual reported cases have more than doubled since 2019, with teenagers accounting for 2/3 of pediatric cases, with over 80% of those poisonings resulting from attempts at self-harm.

Diphenhydramine is a common over-the-counter medication. Its widespread presence in homes poses risk for exploratory ingestion by young children and makes it easily available for misuse to get “high,” or to be taken intentionally in large doses. Adding to its potential danger, diphenhydramine has been part of several risky “challenges” spread on social media. Historically, diphenhydramine has been an important allergy medicine, but newer alternatives are effective and safer, and some organizations are suggesting that diphenhydramine is becoming obsolete.

Diphenhydramine has actions in the body that go beyond the antihistamine effect that is used to reduce itching and hives. It is also anticholinergic and can cause agitation, hallucinations, rapid heart rate, high body temperature, and muscle breakdown. It also works on nerve membranes and can cause seizures, brain swelling, and cardiac arrest. Many families are unaware that the bottle of diphenhydramine in their home can be fatal in overdose.

To reduce injury from diphenhydramine poisoning, the Poison Center offers these tips:

For Families

• Ask your healthcare provider if there are safer choices for treating allergies than diphenhydramine.
• Keep all medications safely stored and dispose of leftover medication when it is no longer needed.
• Buy the smallest amount of medicine to meet your needs - understand that buying bigger bottles leads to bigger risk.
• Speak to family members and healthcare professionals about mental health.

For Health Care Providers

• Consider if newer antihistamines might be better choices for treating patients than diphenhydramine.
• Counsel at-risk teenagers and adults about substance use disorder, and about hazards posed by social media challenges.
• Include poisoning within the context of lethal means restriction counseling.

Several international countries have taken steps to regulate diphenhydramine, and policymakers are encouraged to consider the merit of its continued over-the-counter availability.

Medical care for severe diphenhydramine poisoning is complex, and the experts at the Poison Center are available to assist clinicians, and to teach about potential antidotes for anticholinergic delirium including rivastigmine, physostigmine, and supportive benzodiazepines.

If you suspect that someone may have incorrectly taken diphenhydramine, please call the Children’s Hospital of Philadelphia (or your own regional) Poison Help Hotline at 1-800-222-1222 to be connected to a specialist. If they are having trouble breathing, or having a seizure, call 911. The national Suicide & Crisis Lifeline can be reached by dialing 988.