<prompt> Olopatadine is:Mast cell stabilizerAnti-histamineBoth mast cell stabilizer and anti histamineNone of the above  <response>: Ref: Clinical Oculor Pharmacology, 1st ed. pg. 257 Olopatadine hydrochloride is an antihistamine as well as anticholinergic and mast cell stabilizer It is used as eye drop to treat itching associated with allergic conjunctivitis. Side effects include headache, eye burning andor stinging, blurred vision, dry eyes, foreign body sensation, hyperemia, keratitis and taste perversion. 