Olopatadine hydrochloride ophthalmic solution 0.1% is a topical antiallergic agent that is both an antihistamine with high affinity and selectivity for the histamine H1 receptor and a mast cell stabilizer that inhibits the release of histamine and other proinflammatory mediators from human conjunctival mast cells. The efficacy and tolerability of olopatadine has been demonstrated by several comparative studies in adults and children with seasonal allergic conjunctivitis.