Sunscreens may play an increasingly important role in defending the skin

Jul 21 2005

The benefits of using sunscreen when heading outdoors are well established - protection from overexposure to the harmful effects of the sun, prevention of prematurely aging skin and defense against future skin cancer. Ongoing research about ultraviolet (UV) radiation and its effects on the skin, show how sunscreens may play an increasingly important role in defending the skin.

Speaking at ACADEMY '05, the American Academy of Dermatology's (Academy) summer scientific session in Chicago, dermatologist Elma D. Baron, M.D., an assistant professor of dermatology at Case Western Reserve University, Cleveland, Ohio, discussed how sunscreen benefits the skin now and what it may be able to do in the future.

"The most important thing to know about sunscreen is that, regardless of skin type and ethnicity, everyone needs to use it," advised Dr. Baron. "For basic protection year-round, the American Academy of Dermatology recommends using a broad-spectrum sunscreen - one that protects from both ultraviolet A (UVA) and ultraviolet B (UVB) rays - with a sun protection factor (SPF) of at least 15."

Sunscreens are designed to aid the body's natural defense mechanisms in protecting against harmful UV radiation from the sun. They work by absorbing, reflecting or scattering the sun's rays on the skin. The SPF of a sunscreen is calculated by comparing the amount of time needed to produce a sunburn on sunscreen-protected skin to the amount of time needed to cause a sunburn on unprotected skin. Higher SPF sunscreens offer greater protection from sunburn, which is caused mostly by UVB rays.

Currently, the SPF number on sunscreens only reflects the product's screening ability to protect against UVB rays. At present, there is no approved rating system by the Food and Drug Administration (FDA) that identifies UVA protection. Therefore, Dr. Baron advised looking for sunscreen ingredients which are broad-spectrum (providing UVA and UVB protection). Ingredients that afford good UVB protection are found in almost all sunscreens. Examples of ingredients that afford good UVA protection are titanium dioxide, zinc oxide and avobenzone (Parsol 1789).

"The ingredients within a sunscreen and its SPF number will give consumers an idea of the product's capacity to prevent sunburn, but they do not say much about a product's ability to protect against other harmful effects of UV light," said Dr. Baron. "In the future, sunscreen may be able to prevent UV radiation-induced immune suppression and perhaps prevent the development of skin cancer and photoaging."

UV radiation suppresses the body's immune responses that protect against and fight disease and infection. UV light interferes with the body's immunity, giving cancer cells the opportunity to grow. The development of a sunscreen that could prevent UV-inducted immune suppression, often referred to as the immune protection factor (IPF) of sunscreen, is currently under development. However, there is research available now that shows that sunscreens are already providing protection against pre-cancers. One such study from the New England Journal of Medicine shows that sunscreens prevent actinic keratosis, the earliest stage in the development of skin cancer.

"Increased understanding of sunscreen protection against immune suppression could result in more optimal sunscreens for people who are prone to UV damage and skin cancer," stated Dr. Baron. "Sunscreen with an IPF would greatly benefit fair and light-skinned individuals, organ transplant recipients on systemic immune suppressants and patients with conditions such as xeroderma pigmentosum, where sun exposure is not recommended."

New research has the potential to develop sunscreen that can offer immune system protection and that can greatly enhance the ability to deflect the sun's rays. However, sunscreens are only one part of a comprehensive sun protection regimen and should be used in conjunction with other protective measures.

In addition to wearing sunscreen, and reapplying it every 2 hours, the Academy recommends that everyone be sun smart by following these sun protection guidelines:

• Seek shade whenever possible;
• Avoid outdoor activities between 10 a.m. and 4 p.m. when the sun's rays are the strongest;
• Follow the "Shadow Rule" - if your shadow is shorter than you are, the sun's damaging rays are at their strongest and you are likely to sunburn; and
• Avoid tanning beds.