5 doctors weighed in:

How does Benadryl (diphenhydramine) help reduce allergy symptoms?

5 doctors weighed in
Dr. Giana Nicoara
Internal Medicine - Allergy & Immunology
2 doctors agree

In brief: Reduces histamine

It decreases the amount of chemicals, such as histamine( hence it is an antihistamine), an allergic person's body produces in response to allergens, which could be anything from pollen and pet dander to substances which cause skin rashes.

In brief: Reduces histamine

It decreases the amount of chemicals, such as histamine( hence it is an antihistamine), an allergic person's body produces in response to allergens, which could be anything from pollen and pet dander to substances which cause skin rashes.
Dr. Giana Nicoara
Dr. Giana Nicoara
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1 comment
Dr. Matthew Davis
Benadryl does not directly decrease the amount of histamine, but rather blocks its action as an "inverse agonist" which means it acts at the same place as histamine but does the opposite effect. So if the allergic response was something like a game of tug-of-war, Benadryl will reduce whatever "pull" histamine has. It may be, in this process, that it secondarily reduces amounts of histamine by stopping any further production via the positive-feedback loop that allergies use. Living organisms overwhelmingly prefer negative-feedback loops to positive-feedback loops, because they tend to be unstable and extreme.
Dr. Jack Mutnick
Internal Medicine - Allergy & Immunology

In brief: Antihistamines

It blocks the histamine receptor.

In brief: Antihistamines

It blocks the histamine receptor.
Dr. Jack Mutnick
Dr. Jack Mutnick
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