Sun Exposure

Sunscreens have evolved over the years from thick pasty zinc oxides to cosmetically elegant formulations. Research has shown that sunscreens decrease the extent of sun damage when used properly. There is recent controversy surrounding the use of sunscreens and their potential to promote skin cancer. The truth is that people using sunscreens tend to stay in the sun longer without burning, thus increasing total cell damaging ultraviolet radiation exposure.

Sunscreens usually have good protection from ultraviolet light B (UVB) and fair protection from ultraviolet light A (UVA). Whether or not an individual develops skin cancer depends on the extent of sun exposure, genetic influence, skin type, and number and types of moles.

Sunlight contains wavelengths of UVA, UVB, and UVC. UVC is absorbed by the ozone layer before it can reach the earth's surface. UVB, which consists of shorter wavelengths, is the most abundant and causes sun damage and sunburn. UVA, a longer wavelength, is more penetrating. It can pass through glass and multiple layers of skin. UVA is primarily responsible for premature aging as well as activation of multiple skin enzymes and high-energy radicals that damage skin and can lead to skin cancer.

Most sun exposure is incidental and not from sunbathing. A suntan is in fact sun damage. Darkening of the skin is a defensive response to ultraviolet damage. From a dermatologist's perspective, the only safe tan is from a bottle.

With the abundance of sunscreens on the market, it is difficult to determine which is the most effective, and at the same time, cosmetically acceptable. There are two types of sun protection: sunblocks and sunscreens.

Sunblocks consist of ingredients such as zinc oxide, talc, and titanium dioxide. These preparations form a physical barrier that prevents solar radiation from reaching the skin. Sunblocks are effective for both UVA and UVB ultraviolet exposure. They provide good coverage and usually do not induce allergic reactions. Most of these preparations are waterproof and free of chemicals. Over the last few years, a transparent zinc oxide sunblock has been marketed. This preparation is cosmetically elegant with particles measuring less than 0.1 microns in diameter.

Sunblocks are very effective for sensitive skin. They do not contain many of the chemical irritants seen in other preparations. Many people with medical conditions such as lupus erythematosus, rosacea, or other sun-sensitive conditions benefit from sunblock preparations.

The difference between a sunblock and a sunscreen is that a sunscreen is designed to absorb ultraviolet light. For years, PABA (para-aminobenzoic acid) was the main ingredient for UVB protection. Almost all PABA has been taken off the market due to allergic reactions. Padimate O is a PABA derivative currently used in some sunscreens.

The difference between a sunblock and a sunscreen is that a sunscreen is designed to absorb ultraviolet light. For years, PABA (para-aminobenzoic acid) was the main ingredient for UVB protection. Almost all PABA has been taken off the market due to allergic reactions. Padimate O is a PABA derivative currently used in some sunscreens.

Other UVB sunscreens include the cinnamates (octyl methoxycinnamate and cinoxate). Cinnamates are currently the most widely used ingredient for UVB protection. They are found in moisturizing lotions as well as cosmetic products. Finally, salicylates (homomenthyl, octyl, and triethanolamine) are also used for UVB protection. UVA sunscreens offer added protection. These are benzophenones such as oxybenzone and dioxybenzone. Parsol 1789, methoxydibenzoylmethane, is the best UVA absorber currently available. Most products now contain both UVB and UVA sun protection.

SPF is an acronym for Sun Protection Factor. This translates into the amount of ultraviolet radiation allowed to reach the skin. This is notthe amount of sun blocked. For example, SPF 15 allows 1/15 of the sun's radiation to reach the skin (SPF 30 allows 1/30 of the sun's radiation to reach the skin). Therefore, SPF 15 provides 93% sun protection compared to SPF 30 that provides 96% sun protection. (You can see that little protection is gained from SPF greater than 15).

Recommendations

It is estimated that there would be 78% fewer non-melanoma skin cancers if sunscreen, SPF 15 or greater, were used during the first 18 years of life. Although the advantages to using sun protection from an early age are clear, it is never too late to start protecting yourself.

Recommendations

• Minimize sun exposure during the peak hours of 10 a.m. to 4 p.m
• Wear sunscreen daily. Most sun exposure is cumulative from small, frequent exposures during daily activities. Selecting cosmetics or moisturizers with sun protection makes this easy
• Apply sun-protection 15 minutes before going outside. This allows the lotions to bind to the skin and be more effective. Apply liberally every 3 to 4 hours and after swimming or perspiring
• Use a minimum SPF 15 with UVA and UVB protection. Remember that UVA radiation can pass through car windows
• Use wide-brimmed hats, sunglasses and sun-protective clothing
• Don't forget sun protection for your lips! This is especially important with snow or water sports