I believe I have developed an allergy to antihistamines. I have recently been having the same reaction (stomach pains, gas, diarrhea ) to Benadryl , NyQuil , and Vistaril (even though I have used them long-term) . . .what would be the common ingredient that I am now allergic to? Are there similar drugs that I should stay away from?
Asked On : Wed, 20 Jun 2012