Olopatadine hydrochloride is an antihistamine and mast cell stabilizer, usually sold as a prescription eye drop (0.1% solution, trademark Patanol (or Opatanol in the UK), manufactured by Alcon). It is used to treat allergic conjunctivitis (eye allergies).

It should not be used to treat irritation caused by contact lenses. The usual dose is 1 drop in each affected eye 2 times a day, with 6 to 8 hours between doses.

Its side effects may include headaches (7% of occurrence) burning and stinging (5%), dry eye, foreign body sensation, hyperemia, keratitis, lid edema, pruritus, asthenia, cold syndrome, pharyngitis, rhinitis, sinusitis, and taste change.