Unlike a bulletproof vest, however, sunscreen must be re-applied in order for it to properly provide protection from ultraviolet (UV) rays. Consider the 30-20-2 rule: Apply a SPF 15+ sunscreen to your skin at least 30-minutes prior to going outdoors (even on cloudy days), then reapply within the first 20-minutes of being outside to reinforce the protective barrier the sunscreen provides, and then apply sunscreen consistently in two hour intervals. For children under 18, sunscreen must be applied every hour. The reason sunscreen works in this way is based on the mechanics of our skin.
Our skin works much like a sponge does. The top layer of our skin, called the epidermis, absorbs sunscreen, forming a protective layer on the skin that blocks UV rays from reaching the melanocytes (or "pigmentation cells") that lie deep within the skin. Yet, your skin-the largest bodily organ-reaches its saturation point after approximately two hours, thus leaving you unprotected and causing sunburn and/or other skin-related damage. Hence, it is imperative that sunscreen must be reapplied in order to enhance its protective powers.
Alas, not all sunscreen products out on the market today work proficiently. To deliver optimum level of protection, sunscreen must have sufficient amounts of essential ingredients. In other words, when choosing a sunscreen product for your family, take a look at the bottle; make sure it contains proven effective agents such as zinc oxide and Parasol 1789.
Furthermore, make sure the product is a broad-spectrum formula, meaning that it blocks both UV-B and UV-A rays. If the sunscreen is not broad-spectrum formula, do not buy it. You are not being sufficiently protected nor "covered" if your sunscreen does not clearly indicate that it protects from both UV-A and UV-B rays.
The significance of a broad-spectrum sunscreen cannot be over-emphasized. UV-B and UV-A rays have varied affects on your skin, your immune system, and your body as a whole. UV-B irradiation disrupts the melanocytes (the cells deep beneath the epidermis of your skin responsible for your pigmentation), causing them to release the "redness" known as sunburn.
