Kohala Coast, HI - When talking about photoprotection, we all know we are talking about the entire package, such as seeking shade, using sunscreen and sun protective clothing, and wearing hats and sunglasses, said Henry W. Lim, M.D., while speaking at the Winter Clinical Dermatology Conference.
Kohala Coast, HI
- When talking about photoprotection, we all know we are talking about the entire package, such as seeking shade, using sunscreen and sun protective clothing, and wearing hats and sunglasses, said Henry W. Lim, M.D., while speaking at the Winter Clinical Dermatology Conference.
"The fact that the use of sunscreens can decrease the incidence of skin cancer is, in my mind, by now very clear primarily because of the result of two studies," Dr. Lim said.
In a four-and-a-half-year (and eight-year follow-up) study, 1,621 residents of Nambour, Queensland, were randomly assigned to daily SPF 16 broad-spectrum sunscreen versus control.
The results showed that the incidence rates of squamous cell carcinoma were significantly decreased by 38 percent. Basal cell carcinoma incidence rates decreased by 25 percent, though not significantly, he said.
"So clearly, sunscreen really does decrease squamous cell carcinoma, and maybe even basal cell," Dr Lim said.
Studying the use of sunscreen to prevent photoaging, however, is much more difficult, because changes are subtle and need to be studied over a long period of time, Dr. Lim explained.
Still, several human and animal studies suggest that photoprotection can minimize photoaging, and broad-spectrum sunscreens may actually prevent photoaging, Dr. Lim added.
New developments in sunscreens include photostabilization of avobenzone, a new generation of photostable UV filters, new technologies and oral photoprotection, according to Dr. Lim.
A recent study tested 13 products available in the United States for UVA protection based on in vitro methods. All five products with an FDA "high" (3 stars) rating contained octocrylene and avobenzone (2 percent to 3 percent). None of the products with inorganic UV filters as their sole UVA filters achieved a "high" rating, nor did any of the products with oxybenzone as the only UVA filter, as they do not cover long-wave UVA very well, Dr. Lim said.
"Photostabilized avobenzone is crucial to achieve good broad-spectrum protection," he said.
In addition, combining organic and inorganic filters can achieve a higher SPF.
Dr. Lim said that SunSphere, which is a styrene/acrylates co-polymer with a 325 nm diameter, is nearly invisible and cannot be felt during application. It is filled with water, which then migrates out when applied to the skin. The hollow beads then scatter UV rays. SunSphere with an organic filter is capable of boosting SPF by 50 percent to 70 percent, according to Dr. Lim.
Oral photoprotection in the form of Polypodium leucotomos, which has been around for some time, is a fern plant extract from Central America that has an antioxidant and anti-inflammatory effect, though SPF is a low 3 to 8, leaving it as a less promising option.
"This product is not functioning as a sunscreen with such a low SPF," Dr. Lim said. DT