The Scoop on Sunscreen, Part 1

Summer time is fast approaching, and although here in St. Louis glimpses of the sun recently have been far and few between, sunny days will return to us eventually. Although the use of sunscreens shouldn’t be reserved for just sunny, summer days, this is definitely the time of year when they are foremost in most people’s minds. Of course, if your concern includes the prevention of premature aging skin, you probably think about sunscreen year round, because UVB/UVA radiation is the primary preventable cause of aging skin.

To protect your skin from both types of radiation (UVB and UVA), a sunscreen must contain a combination of organic (chemical sunscreen ingredients) and inorganic (physical sunscreen ingredients) filters. Combination sunscreens enhance the SPF of the final product.

Chemical sunscreen ingredients act as an ultraviolet sponge to absorb damaging UV rays. The chemical reaction of the UV rays with the chemical sunscreen ingredient creates heat, which is why some people experience “feeling hot” when using sunscreens. Physical sunscreen ingredients deflect or block damaging UV rays in a similar fashion to protective clothing.

Current toxicology based on acute and chronic exposure to (UVB/UVA) broad-spectrum sunscreens concluded that sunscreen ingredients or products pose no human health concern, despite what may be reported in the media. What is a positive, as well, is that micronized, transparent zinc oxide is not absorbed into the skin; and there are no reports of skin allergies to zinc oxide.

Most dermatologists would agree that the use of sunscreen has contributed to a decrease in the incidence of photo-damage and pre-cancerous skin lesions. In fact, the American Academy of Dermatology recommends that, regardless of skin type, a broad-spectrum sunscreen with an SPF of at least 15 should be used year-round. Patients must understand that sunscreen shouldn’t be reserved for use only on sunny days. Seventy percent of the sun’s ultra-violet rays can pass through the clouds. Additionally, sand reflects 25 percent of the sun’s rays, and snow reflects 80 percent of the sun’s rays.

SPF is an indication of a sunscreen’s effectiveness in preventing sunburn related to the length of time in the sun, but it does not actually increase proportionately. An SPF of 35 blocks 97-98 percent of the UVB rays, while an SPF of 15 blocks 93 percent of the rays, and an SPF of 2 screens 50 percent of the UVB rays.

SPF only relates to a sunscreen’s ability to block UVB rays. Unfortunately, at the present time there is no measure to quantify the effectiveness of a sunscreen’s ability to block UVA rays. It is well known that chemical sunscreen ingredients that block UVA rays are somewhat unstable when exposed to UV rays and oxygen (air). This is further complicated by the fact that we do not have the ability to measure the stability or effectiveness of chemical sunscreens that block UVA rays.

The most reliable and effective ingredients for protecting the skin from UVA rays are physical sunscreen ingredients. Zinc oxide and titanium dioxide are the two physical blockers used here in the United States. Unlike years ago when physical blockers looked like a white paste on your face, nanotechnology has eliminated this problem by creating micronized particles of zinc oxide and titanium dioxide. Micronized zinc oxide and micronized titanium dioxide are transparent when applied to the skin.

The ideal sunscreen must be broad spectrum; that is, containing agents that can provide protection from both UVB and UVA radiation.

All FDA-approved sunscreen ingredients have a particular absorption spectrum. The ideal sunscreen would combine ingredients to expand the range of ultraviolet protection from damaging ultraviolet rays and should include either micronized zinc oxide or titanium dioxide, given the lack of knowledge regarding the effectiveness of chemical UVA blockers. In addition, it has been shown that daily use of a sunscreen increases its photo-protection, as sunscreen ingredients can bind to skin cells in the outer layer of the skin.

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