Educational only — not medical advice. If you’re in crisis or thinking about suicide: call or text 988 (U.S.) or your local emergency number. Support resources. Under construction and review—see the updates log.
Brand: BENADRYL
Published 2026-02-05 · Last reviewed 2026-02-12 · 4 references
Content sourced from FDA labeling (DailyMed) and peer-reviewed literature.
Diphenhydramine (brand Benadryl) is a first-generation antihistamine used OTC for allergy symptoms and commonly used as an OTC sleep aid.
It is strongly Anticholinergic as well as sedating. In psychiatry, that combination can make it appealing for short-term insomnia or acute distress, but it also increases delirium, constipation, and urinary retention risk—especially in older adults and in polypharmacy (Beers / clinical).
Evidence for chronic insomnia benefit is limited, and the AASM guideline recommends against routine diphenhydramine use for chronic insomnia (weak recommendation). Treat it as a time-limited adjunct while addressing underlying drivers (mood episodes, substances, pain, sleep apnea, circadian disruption).
Next-day impairment is a key limiter: driving impairment, falls, and cognitive slowing can occur, particularly with higher doses or when combined with other sedatives (clinical).
The diphenhydramine compare view, evidence feed, and print page support shared decision-making around OTC sleep aids and safer alternatives.
Diphenhydramine is inexpensive and widely accessible, which can lead to “refill momentum” as a nightly sleep aid. In older adults, Beers Criteria guidance generally supports avoiding chronic first-generation antihistamine use because anticholinergic harms often outweigh benefits.
View labelExactRefer to the Glossary entry on Neurotransmitters for background on receptor systems involved in serious mental illness.
H1 antagonism reduces histamine signaling and produces sedation (central H1 blockade).
Antimuscarinic (anticholinergic) activity contributes to dry mouth, constipation, urinary retention, blurred vision, and delirium risk.
Sedation can feel helpful for sleep onset, but it does not treat the underlying insomnia system; tolerance and diminished benefit can occur with repeated nightly use (clinical).