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A member asked:

What are the side effects of antihistamines and what can we do about each?

A doctor has provided 1 answer
Dr. John Chiu answered

3rd generation AH: Older antihistamines (AH) like Benadryl, (diphenhydramine) Atarax , Periactin caused drowsiness and dry mouth in at least 30% of the people. Weight gain in another potential side effect. Newer antihistamines like Zyrtec, Xyzal causes drowsiness in about 10% of the people 3rd generation AH like Allegra and Claritin are not expected to cause drowsiness in 95% of the people.

Dr Fowler and another doctor agreed

Answered 10/3/2014

3.7k views

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