The sun gives off invisible rays of ultraviolet light. Ultraviolet B (UVB) rays are short, high-energy wavelengths that are absorbed by the epidermis, the outermost layer of the skin. When you burn, the skin responds to UVB rays by producing chemicals called inflammatory mediators, some of which seep down into the dermis, the skin’s middle layer. These chemicals irritate the tiny blood vessels in the dermis, which swell and create the surface redness of the burn. At the same time, the UVB rays affect the genetic material of the epidermis, which causes the damage that may lead to skin cancer. Other UVB rays can affect the immune system and interfere with the skin’s ability to repair itself. Finally, UVB radiation attacks the skin’s melanocytes (pigment cells).
Ultraviolet A (UVA) rays – longer than UVB rays – can also do lasting damage. They penetrate the skin more deeply than UVB rays, affecting the DNA of the cells in the dermis, attacking cell membranes, and changing the proteins that make up collagen and elastin, which support the skin’s fibrous structure. By undermining these parts of the skin, UVA rays lead directly to wrinkles and sagging of the skin.
The best protective clothes are loose fitting garments made from fabric that is tightly woven. Darker colors may offer more protection than light-colored clothing, and dry clothes provide better protection than wet ones. A wide-brimmed hat that offers a lot of shade is the best choice for protecting head, face and neck. If long pants and a long sleeved shirt can’t be worn because of the temperature, it is important to wear a dry T-shirt, stay in the shade as much as possible, and always wear sunscreen.
Sunscreens provide protection by absorbing, reflecting or scattering the sun’s rays. They may also contain chemicals that interact with the skin to protect it from UV rays. Sunscreens are rated according to their effectiveness by the sun protection factor (SPF). A product’s SPF number helps determine how long the product will protect you before you need to re-apply it – how long you can stay in the sun without burning.
Sunscreens with SPF numbers higher than 15 may work well for people who have lightly pigmented skin, live at high altitudes, or work or play outdoors much of the day. To get the most protection from your sunscreen, apply it liberally at least 30 minutes before going outside and remember to re-apply it after swimming or perspiring heavily. You should always wear a sunscreen with at least SPF 15, no matter what your skin color. Even people with very dark skin can burn and develop skin cancer.