Sun exposure can cause both acute and chronic injury to the skin. It is well documented that long-term sun exposure, with or without sunburn, can cause harmful effects. Long-term sun exposure has been associated with premature aging of the skin, malignant changes in the skin, development of lip cancer and corneal opacities. Skin cancer is the most rapidly increasing form of cancer in the United States. Recent studies indicate that the incidence of skin cancer is increasing at an alarming rate with 600,000 new cases being reported every year. One in five Americans will develop skin cancer in their lifetime. Skin cancer diagnosed in the early stages has almost a 100 percent cure rate. Any unusual bumps, spots, or patchy areas on the skin without a known cause should be examined by a doctor.
Physical sunscreens are thick, solid colored substances, that are very effective in blocking both UVA and UVB radiation; however, they are messy and usually cosmetically unappealing.
Chemical sunscreens are the most commonly used and are available in a variety of formulations. They contain one or more of the UV radiation-absorbing chemicals. Some of the most widely used chemical groups that block UVB radiation are PABA (p-aminobenzoic acid), PABA esters (padimate O), cinnamates (cinoxate, ethylhexyl-p-methoxycinnamate), salicylates (octylsalicylate, homosalate), and anthranilates (methyl anthranilate). While these all block UVB radiation, the chemical group known as benzophenone (oxybenzone and dioxybenzone) provides protection against both UVA and UVB radiation.
Sunscreens have been assigned Sun Protection Factor (SPF) values by the U.S. Food and Drug Administration (FDA) since 1978. SPF is a number that refers to the sunscreen products ability to block UVB radiation. Sunscreen products with SPFs of 2 to 50 are currently available. A sunscreen product with a SPF of 15 will protect your skin 15 times longer from UVB than if you did not have sunscreen applied. The exact amount of time will vary from person to person, the altitude, and proximity to the equator. SPF 15 will block 95% of the UVB wavelengths. SPF 30 does not work twice as well. SPF 30 will provide another 3% of protection.
The efficacy of a product is related not only to its SPF but also to the ability of a sunscreen to remain effective under the stress of prolonged exercise, sweating, and swimming. The following three labeling recommendations have been suggested to help the ability of a sunscreen to remain effective:
It is recommended that sunscreens be reapplied after swimming or perspiring. However, reapplication of a sunscreen does not further the period of protection.
The American Academy of Dermatology, the American Academy of Pediatrics, and the Skin Cancer Foundation recommend that protection from excessive sun exposure be initiated early. Regular use of an SPF-15 product starting after 6 months of age and continuing through 18 years can decrease the incidence of skin cancer over a lifetime by as much as 78%.
Radiation from the sun is most damaging between the hours of 10 a.m. and 2 p.m. Sun exposure should be avoided during this time whenever possible.
The individuals skin type is an important factor that must be considered when attempting to choose a sunscreen with the appropriate SPF. In general, very fair-skinned individuals or those with previously sun-damaged skin may benefit from high SPF products. None of the available sunscreen products are recommended by the FDA for use on children under 6 months of age. In addition, products with an SPF of four or less are not recommended for use on children under 2 years of age because they will not provide adequate sun exposure protection.
Sunscreen should be applied 20 to 30 minutes before sun exposure so the product has a chance to bond with the skin. Products containing PABA and PABA-like chemicals, however, may need to be applied up to two hours in advance of sun exposure in order to achieve their maximal effect.
Using an adequate amount of sunscreen provides greater sun protection than using an inadequate amount of a sunscreen with a higher SPF rating. Most individuals do not apply enough sunscreen to achieve adequate protection.
No sunscreens should be used on children during the first 6 months of life.
Sunscreens that contain aminobenzoic acid and its esters (PABA), cinnamates, and oxybenzone can cause a skin rash and allergic photosensitivities but this is uncommon. In May 1988, a new nitrosamine known as NPABAO was found in certain sunscreens containing padimate-O as the active ingredient. Nitrosamines themselves can be carcinogenic; however, at this time it is uncertain whether this nitrosamine is present in sufficient quantities in sunscreens to be of concern.
Miscellaneous compounds, such as fragrances, lanolin, alcohol, and preservatives may also cause skin and eye irritation or sensitization.
Symptoms are unlikely with normal childhood exposure. Stomach irritation and nausea are the most common symptoms. Since spray sunscreens contain 50% or more ethanol, alcohol toxicity may be the greater risk.
Many sunscreen products contain a form of an aspirin-like substance (salicylate) as their active ingredient. For example, homomenthyl salicylate (homosalate) is a sunscreen agent found in many Coppertone products. Theoretically, homosalate-containing sunscreens ingested in substantial amounts may cause aspirin (salicylate) poisoning; however, there are no such reported cases of salicylate intoxication.
The risks of sun exposure and its relationship to skin cancer have been well documented. Regular sunscreen use seems to help limit these harmful effects. The risks of using sunscreen products appear to be minimal. Therefore routine sunscreen use should be recommended in all individuals, especially children, exposed to the sun.