Across 116 first-hand reports, people mentioned a side effect 52 times (about 45 per 100 reports). The most common: drowsiness, brain fog, anticholinergic. User reports show what people notice — they can't tell you whether Diphenhydramine is safe for you.
“Benadryl works the best when there is nothing else I can do and I take it a lot but probably not the best way to get sleep.”
“i can't sleep at all when i take that stuff. Makes me paranoid.”
“Had insomnia and tested out a Benadryl and trazadone. Felt weird and nervous but it let me sleep at least.”
“Does put me to sleep pretty well, but I wake up the next day feeling drowsy and horrible. Also not a great supplement for an athlete to take due to causing heat intolerance.”
“I have had experience with diphenhydramine but it ended with less than normal sleep.”
“I'd also cut Diphenhydramine, I suspect that it cant be good long term...Diphenhydramine is not an ideal sleep aid. May impact your memory into the following day.”
Conclusion: The studies in this review suggest hydroxyzine could be considered as a short-term treatment option for adults with insomnia for whom previous therapy was ineffective, not tolerated, or contraindicated. Additional long-term studies with an active comparator are needed to further establish its role in insomnia treatment.