Sunscreen should be applied liberally to clean, dry skin at least 20 minutes before going outside. This allows the sunscreen to adhere to the skin surface and function properly. As sunscreens wear off the skin with normal usage, it is necessary to re-apply the product frequently to maintain your protection. Re-application is recommended should the sunscreen be worn off the skin through such actions as: exercise, swimming, towel drying the skin after swimming or blowing the nose.