Dr. Henry W. Lim, chairman of the department of dermatology at Henry Ford Hospital and Clarence Livingood lecture, from Detroit recently spoke at the American Academy of Dermatology in San Francisco on the safety of sunscreens. Here’s some of the things he said.
Are the ingredients of sunscreens safe? Benzene like derivatives were once used and are only rarely now, as they have been implicated in causing cancers in laboratory animals. Newer ingredients have replaced them. These cover the full spectrum of light – from the burning rays – UVB – to the aging rays – UVA.
One of the newer ingredients is avobenzone, a marvelous UVA blocker. Alone, it is not stable and converts to a free radical which can damage other tissues. However, when used with other agents, it is stabilized, safe and completely able to block the aging effects of sunlight. Other new generation agents which do this include include methoxoryl, and methoxoryl L. Many other ingredients have high molecular weights so won’t pass through the skin and have little effect in damaging deeper structures.
That’s true of many of the physical blocking agents like titanium dioxide and many of the newer chemicals used to absorb sunlight.
Other new ingredients in sunscreens include microspheres – tiny little beads – which serve top diffract and scatter the sunlight. And another ingredient is currently out for internal and external use – a fern plant extract which has powerful antioxidant and anti inflammatory properties. This has an SPf of 3-8.
Are there new sunscreens out? The newest are soap bars that leave a polymer and sunscreen behind. Unfortunately, they currently have a rather low SPF so cannot be endorsed. With time, however, they may evolve to useful agents.
Do sunscreens prevent cancer? It is fairly certain that sunscreens prevent burns (erythema). It is also fairly certain that they decrease the number of actinic keratoses, which cause a type of cancer called squamous cell carcinoma. They also decrease photo-aging as demonstrated by decreasing the number of red spots, brown sapots and wrinkles. An Australian study which followed people for 10 years clearly demonstrated this. They also demonstrated that they decrease basal cell carcinomas by about 25%. In this study, this did not reach statistical significance, but probably would if more people were in the study or if they study were increased for a longer period of time. The thing we cannot show at the current time is that melanoma is prevented by sunscreen.
Do sunscreens cause harm? One recent study, done by the EWGgroup, waswidely quoted in the press, stated over 952 products contained ingredients that were harmful. That is, these ingredients changed into free radicals which can damage normal tissue. This may be true when each ingredient taken alone, but the study did not study the entire sunscreen product, so their conclusion is not valid.
Also, some studies have found oxybenzone in the urine of sunscreen users. The significance of this is not known. Finally, some studies have shown that sunscreens cause estrogen like side effects in laboratory rats. This has not been demonstrated in humans.
However, sunscreens do affect the production of D3 which is made in the skin. Most experts agree that individuals should take a supplement of this of about 1,000 to 2,000 units a day.