Whether you have been newly diagnosed with mast cell activation syndrome (MCAS) or if you have been struggling for years, you likely have been provided the same basic treatment options. Most patients are first offered Histamine 1 blockers (H1 blocker) which are antihistamines including Claritin, Allegra, Zyrtec, Xyzal, Benadryl and Hydroxyzine. Typically, a histamine 2 blocker is then added which is usually Pepcid now that Zantac is off of the market. If these medications at appropriate doses are insufficient, mast cell stabilizers such as cromolyn sodium and ketotifen (really both a mast cell stabilizer and an H1 blocker) are used.