Is it ok to take three different antihistamines?

Possibly OK.: It probably won't hurt you, but you gotta wonder if it is helping you. I can imagine combinations of a topical antihistamine, a good general non sedating oral antihistamine, and a traditional sedating antihistamine .

Not a good idea: Unless specifically instructed by an allergist. I have only seen people on more than one antihistamine for severe recurrent hives (urticaria). Taking too many antihistamines at once can cause issues with urinary retention and other problems.