Ketotifen Fumarate is a kind of anti-histamine eye drop, utilized for providing relief from itchy eyes caused by allergic or seasonal conjunctivitis. Also, it works as a mast cell stabilizer that prevents allergic reaction by decreasing the natural substances that cause allergic reaction. Use it as exactly as directed by your doctor. Generally, Ketotifen Fumarate is used two times in a day (every 8 - 12 hours) one drop at a time. For best results, use it everyday until you are no longer exposed to the allergic substance.