What is the best over-the-counter antihistamine? I'm Dr. Manan Shah, I'm an ENT and allergist with Wyndly Health. The best antihistamine depends on what you need. So, the fastest-acting antihistamine is Cetirizine, otherwise known as Zyrtec. That's going to get into your body within 15 to 20 minutes and start working. But it can make you somewhat drowsy.
So the least sedating antihistamine is Fexofenadine, otherwise known as Allegra. And that one is going to keep you from feeling drowsy and foggy. So it really depends on what you want. I tell my patients to try Claritin, Allegra, and Zyrtec and figure out which one works best for your body. Thanks.