Normal cellular aging in humans leads to reduced tear production. In fact, it is estimated that between the ages of 10 and 40, tear production is reduced by 50%. In addition, other common causes of dry eye are eye infections (conjunctivitis, corneal ulcers, etc.), external or environmental factors (sun, wind, chlorine, contact lenses, etc.) and certain medication. Cosmetics and cleansing creams can also cause irritation and disrupt tear production.