The surface of your eye is covered by a thin layer of tears, called the Tear Film which protects, nourishes and lubricates the eye. Allergens can enter the tear film causing irritation to the ocular surface. These allergens can cause red, itchy and watery eyes. OPTASE Allergy Eye Drops contain a natural molecule called Ectoin which helps both to flush allergens from the eye and protect from harmful allergens entering the tearfilm.