Hypromellose is used to treat reduced or deficient tear production. Hypromellose lubricates the surface of the eye just as natural tears would do, relieving dryness & pain. The active substance is hypromellose 5 mg/ml (0.5%). Other ingredients: benzalkonium chloride as preservative, sodium citrate, disodium hydrogen phosphate anhydrous, sodium dihydrogen phosphate monohydrate, sodium chloride & purified water. Isopto Plain is supplied in a 10 ml dropper bottle. Warning: Do not use if your pet has a known sensitivity or allergy to any of its ingredients.