When properly applied, Derma Shield lasts for up to 4 hours even after repeated washings. It helps maintain the skin's natural moisture balance and allows the skin to breathe and perspire normally. Derma Shield is safe for all skin areas. It is clinically and laboratory tested, is CFC-free and can be used underneath gloves. The 17 ounce (500 mL) size is the most popular, and will last over a year if used twice daily per instructions.