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How long does Benadryl take to work?

Medically reviewed by Carmen Pope, BPharm. Last updated on April 21, 2023.

Official answer

by Drugs.com

Benadryl is quickly absorbed after oral administration and it starts to work within 30 minutes with peak effects reached within one to two hours. The effects of Benadryl last from four to six hours. Benadryl in the injectable form has a rapid onset of action. You will know when Benadryl starts to work because your allergy symptoms, such as congestion, runny nose, itchy eyes, or a skin rash, will start to feel better.

References
  • Benadryl Injection [Package Insert]. Revised 04/2021. Parke-Davis. https://www.drugs.com/pro/benadryl-injection.html
  • U.S. National Library of Medicine MedlinePlus. Antihistamines for allergies. Available at: https://medlineplus.gov/ency/patientinstructions/000549.htm.

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Benadryl (generic name: diphenhydramine) is an antihistamine that causes sleepiness in most people. Some people use Benadryl to help with sleep or insomnia, but this should only be for short-term use. Do not use Benadryl to make a child sleepy. Contact your doctor if you or your child are having trouble with sleep. Continue reading

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