QUESTION & ANSWER
Q: Why does Benadryl make you sleepy?

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A:

Benadryl (diphenhydramine) blocks the chemical histamine. Histamine is involved in causing allergy and cold symptoms. It also plays a role in wakefulness. When Benadryl blocks histamine, it takes away its stimulation of wakefulness. Many people experience this as drowsiness and can use Benadryl to sleep.

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  1. Diphenhydramine. U.S. National Library of Medicine. https://medlineplus.gov/druginfo/meds/a682539.html
  2. Thakkar MM. Histamine in the regulation of wakefulness. Sleep Med Rev. 2011;15(1):65–74.