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A female asked:

How long does it take for benadryl to take effect?

1 doctor answer2 doctors weighed in
Dr. Charles Cattano
Gastroenterology 40 years experience
Some variables here: IV is faster than oral, but what dose and for what indication (sleep, rash, allergy, etc.) are you questioning please.

Similar questions

A 49-year-old member asked:

How long does the effect of children's Benadryl (diphenhydramine) last?

1 doctor answer3 doctors weighed in
Dr. Eric Goldstein
Pediatrics 23 years experience
Benadryl (diphenhydramine): Typically, 4-6 hours.
A 46-year-old member asked:

How long does it take Benadryl (diphenhydramine) to get out of your system?

1 doctor answer2 doctors weighed in
Dr. Jeffrey Rumbyrt
Allergy and Immunology 33 years experience
4-6 hours: Typically, the effect of Benadryl (diphenhydramine) is 4-6 hours. It may be longer in people with liver disease.
A 41-year-old member asked:

How long does it take for Benadryl (diphenhydramine) to leave the body?

1 doctor answer2 doctors weighed in
Dr. Andrew Oswari
Family Medicine 25 years experience
Half life is 8 hours: Its effectiveness only lasts 6-8 hours usually. It's half life is 8 hours, so it may take up to 72 hours to leave your system completely.
A 32-year-old member asked:

How long does it take for liquid Benadryl (diphenhydramine) to wear off?

1 doctor answer2 doctors weighed in
Dr. Jeffrey Rumbyrt
Allergy and Immunology 33 years experience
4-6 hours: Typically, the effect of Benadryl (diphenhydramine) is 4-6 hours. It may be longer in people with liver disease.
A 37-year-old member asked:

How long does it take for Benadryl (diphenhydramine) to make you drowsy?

1 doctor answer2 doctors weighed in
Dr. Tammi Schlichtemeier
Pediatrics 32 years experience
About 45 minutes: Benadryl (diphenhydramine) can make some people drowsy. The maximum effect occurs in about 45 minutes or so. However, it can result in hyperalertness in some people.

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Last updated Mar 16, 2021
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