AgingSkinNet Article
Protection Against Photoaging

"Photoaging" is the term that describes damage to the skin caused by intense and chronic exposure to sunlight. The visible effects of photoaging are fine wrinkles, mottling and pigmentation of the skin, and skin roughness—changes that are usually associated with chronologic aging (calendar years). But, photoaging is not a good indicator of chronologic age; it just makes a person to look older than his or her chronologic age. The three approaches to counter photoaging are:

  1. Avoid the midday sun

  2. Prevention by use of photoprotective agents—sunscreen and clothing

  3. Skin rejuvenation treatments (Click on Cosmetic Procedures)

Photoprotection is the use of physical and/or chemical agents to prevent the skin-damaging effects of ultraviolet (UV) radiation in sunlight. Physical agents are clothing, umbrellas and parasols, awnings and tents that protect you from sun when you are outdoors. Chemical agents are sunscreens you apply to your skin.

The effects of UV radiation on the skin are related to the intensity and duration of UV exposure. Avoiding intense, chronic exposure to solar radiation—for example, avoiding activities such as sun bathing—is one important way to protect against photoaging. Photoaging can be minimized by avoiding sun exposure between 10 AM and 4 PM. If you cannot avoid sun exposure between these peak hours of UV intensity, use sun-protective measures such as wearing a broad-brimmed hat and long-sleeved sun-protective clothing. You also need a broad-spectrum sunscreen with SPF 30 or higher if you are going to be exposed to sunlight for more than 20 minutes. An important point to remember: Even on cloudy days, 80 percent of the sun’s UV rays reach the ground. A cloudy day is not a reason to skimp on photoprotection.

Photoprotective Topical Sunscreens
There are two basic types of topical sunscreens:

  • Absorbers of UV radiation—chemical sunscreen ingredients such as para-amino benzoic acid (PABA), cinnamates, salicylates and benzophenones

  • Reflectors of UV radiation—physical sunscreen ingredients such as titanium or zinc oxide

A third class of topical agents is the antioxidants such as vitamins E and C that do not absorb or reflect UV radiation but are believed to enhance the ability to skin cells to repair damage induced by UV radiation.

Sunscreens usually consist of a combination of several photoprotective chemicals. The degree of protection they provide is measured as a sun protective factor (SPF). Persons who always burn rather than tan—typically a person with pale white skin, red or blond hair, and blue or green eyes—are at highest risk for photoaging and skin cancer and should always use maximum photoprotection. Dermatologists strongly recommend a broad-spectrum sunscreen with SPF of 30 or higher for all skin types. SPF is determined in the United States by a guideline accepted by sunscreen manufacturers and the Food and Drug Administration (FDA). Topical sunscreens are marketed as lotions, creams, gels and ointments; the type you choose is a matter of personal choice.

An effective sunscreen should also be broad-spectrum, providing protection against both the A and B wavelengths of UV. Both UVA and UVB are present in sunlight and both can cause skin damage. The UVB wavelengths are the principal cause of sunburn. UVA can penetrate to deeper layers of the skin. Since most chemical ingredients of sunscreens are most effective against either UVA or UVB, many sunscreens are a mixture of UVA and UVB-absorbing chemicals, or physical blocking agents such as zinc oxide. You can check the label to see if a sunscreen provides both UVA and UVB protection. A sunscreen providing only UVB protection is effective against sunburn but less effective against the deeper penetrating UVA. You can also check the label of a sunscreen product to see if it contains ingredients that provide broad-spectrum (UVA-UVB) protection—e.g., oxybenzone, cinnamates (octylmethyl cinnamate and cinoxate), sulisobenzone, salicylates, titanium oxide, zinc oxide, and avobenzone (Parsol 1789).

Suggestions to improve sunscreen effectiveness:

  • Apply sunscreen 20 minutes before you go outdoors

  • Use about 1 ounce (enough to fill a shot glass) to cover the entire body. Cover all exposed areas liberally. Pay special attention to face, ears, nose, arms and legs. Remember that lips can burn, too, so cover lips with a lip balm sunscreen or SPF 30 or higher

  • Reapply approximately every 2 hours, or after swimming or heavy sweating (reapplying does not increase the SPF—it just keeps the SPF at its maximum level)

Broad-spectrum sunscreens with SPF or 30 or higher and both UVA and UVB protection are effective in preventing actinic keratoses (AK), skin conditions that can be a precursor to skin cancer. Effective sunscreen protection may also help to prevent the development of melanoma, the most deadly skin cancer.

Side effects of sunscreens, if they occur, are usually a contact irritant reaction to a chemical in the sunscreen. Other possible side effects include phototoxicity or photoallergy (due to interaction of chemicals in the sunscreen with sunlight), and contact allergy. A sunscreen that causes a side effect should be avoided. Persons with an existing skin condition such as acne, eczema or other dermatitis, actinic keratoses or rosacea should consult a dermatologist regarding selection of an appropriate sunscreen.

In Summary: Criteria for Selecting a Sunscreen to Prevent Photoaging

  • SPF of 30 or higher

  • Broad-spectrum, providing both UVA and UVB protection

  • Does not cause skin irritation

  • Does not worsen an existing skin condition

  • Selecting Clothing for Photoprotection

For maximum photoprotection you can select clothing as well as sunscreen on the basis of SPF. Clothing with a high SPF can block nearly 98 percent of UVA and UVB radiation—a degree of protection especially important (1) if you burn easily and are at high risk for photoaging, skin cancer and other sun-induced skin conditions, and (2) if you spend a lot of time in the sun while hiking, fishing, gardening, and working outdoors. Good sun protection is important for children, also. Skin damage can begin early—80 percent of sun exposure is received before age 18. Some epidemiologic studies have indicated that heavy sun exposure in childhood is a risk factor for melanoma (the deadliest form of skin cancer) later in life.

For maximum photoprotection from clothing:

  • The clothing should provide maximum body coverage—long pants, long-sleeved shirt, and wide-brimmed hat

  • Tightly woven synthetic fabrics made from nylon and polyester provide maximum protection. Tightly woven cotton blends are nearly as UV protective and more comfortable in high heat and humidity

  • Fabrics made specifically to provide UV protection are made by U.S. manufacturers to meet SPF specifications. A SPF of 30 or higher provides adequate UV protection

  • A dermatologist can make recommendations regarding selection of sun-protective clothing for the needs of the individual patient

Skin Color and Risk for Photoaging
Skin tends to be more susceptible to photoaging on the basis of skin color. In general, the fairer, less pigmented the skin, the greater the risk for photoaging and other sun-induced skin problems, including skin cancer:

Fitzpatrick Classification of Skin Type
I -   Always burns, never tans (pale white skin)

II -  Always burns easily, tans minimally (white skin)

III - Burns moderately, tans uniformly (light brown skin)

IV - Burns minimally, always tans well (moderate brown skin)

V -  Rarely burns, tans profusely (dark brown skin)

VI - Never burns, (deeply pigmented dark brown to black skin)

A person whose skin meets criteria for Type 1 is likely to be a person with pale white skin, red or blond hair, blue or green eyes, and Celtic (Irish, Scottish, Welsh, Breton) ancestry. This description fits a significant fraction of the United States population. A person with Type 1 skin is very sensitive to UV radiation, burns easily, never tans, and is at risk for early onset of skin damage that results in photoaging.

Skin Types II and III are increasingly more pigmented shades of white, with tendency to burn rather than tan, and moderate to strong risk for photoaging and other sun-induced skin problems.

Types IV and V are "olive" to moderate brown in skin color, sunburn minimally and tan easily, and have moderate to low risk for photoaging and other sun-induced skin problems.

Type VI is dark brown to black in skin color, never sunburns, and has a minimal risk for photoaging. Risk for skin cancers related to sun exposure is very minimal.

Dark-skinned persons and white-skinned persons are, however, equally at risk for dehydration with long-duration sun exposure.

World-wide statistics on skin cancer have led dermatologists to recommend broad-spectrum sunscreen of SPF 30 or higher for all skin types.

References:
•  AAD "Dermatology Insights" Spring 2000.
•  AAD Facts About Sunscreens.
•  AAD Guidelines for Photoaging/Photodamage.
•  Pathak MA et al. Sun-protective agents: formulation, effects, and side effects. In: Freedberg I M et
    al (Eds.). Fitzpatrick’s Dermatology in General Medicine, 5th ed. New York: McGraw-Hill;
    1999:2742-2763.

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