What olopatadine eye drop is used for: Olopatadine eye drop is a medicine for treatment and control of allergic conditions of the eye. It works in two different ways by reducing and controlling the intensity of the allergic reaction.  Olopatadine eye drop is used for the treatment of itchy eyes associated with seasonal allergic conjunctivitis. Allergic conjunctivitis: Some materials (allergens) like pollens, house dust or animal fur may cause allergic reactions resulting in itching, redness as well as swelling of the surface of your eye. Do not use olopatadine eye drop if: • Olopatadine eye drop should not be used if you are allergic to olopatadine hydrochloride or any of the other ingredients Do not use Olopatadine eye drop in children under the age of 16 years. Warnings and precautions: Before you use Olopatadine eye drop talk to your doctor or pharmacist.  Use of Olopatadine eye drop and use of contact lenses  • Do not wear contact lenses if your eyes are red.  • Olopatadine eye drop contains a preservative, benzalkonium chloride, which may cause eye irritation and is known to discolor soft contact lenses. Do not use the drops while wearing contact lenses.  • Remove your contacts before applying Olopatadine eye drop and wait at least 15 minutes before putting your contacts back in.  Possible side effects A small number of people who use Olopatadine eye drop may get side effects. They can be unpleasant, but most of them disappear rapidly. You can usually continue using the drops, unless the effects are serious. If you're worried, talk to a doctor or pharmacist. Side effects may include:    • dry, itchy, red, irritated or crusted eyes  • eye surface inflammation  • eye discharge  • eye pain  • increased tear production  • eyelid redness, swelling  • sensitivity to light  • blurred vision  • staining in your eye  • burning, stinging or gritty feeling • headache  • dizziness  • fatigue or tiredness  • nasal dryness  • increased heart rate  • a dry mouth  • a change in your sense of taste  • nausea  • red or itchy skin