Professional Advice - Central Texas Dermatology
Choosing a Sunscreen
There is so much confusion about sunscreens. No wonder, considering the fact that there are close to five thousand sunscreens on the world-wide market. This hand-out will discuss the magnitude of the skin cancer problem in the United States, controversial safety issues and, finally, recommendations to help you choose a sunscreen for you.
Despite the fact that the incidence of most cancers is decreasing in the United States, skin cancer numbers continue to rise. In fact, we are in the midst of a skin cancer epidemic. One in five people will develop skin cancer, that is 3.5 million patients per year. Most worrisome is the marked rise in malignant melanoma rates, especially in younger patients. The cause? Tanning beds. The World Health Organization (WHO) has documented a 75% increase in malignant melanoma due to tanning bed usage. In teenagers and young adults between the ages of fifteen and twenty-nine, it is the second most common cancer. The five billion dollar per year tanning bed industry would have you believe that a base tan will prevent subsequent burning and yet a base tan only provides an SPF of 2.5. They also claim benefits from vitamin D production in the skin. More on that later.
The safety of three sunscreen ingredients has been challenged in recent years: oxybenzone, retinyl palmitate and nanoparticles present in zinc oxide and titanium dioxide.
Oxybenzone has been used in sunscreens since 1978. It is an excellent blocker of both UVA and UVB. Some claim that it may cause hormonal abnormalities, specifically estrogen - like effects. Although this has indeed been shown in lab studies, these studies have limited applicability to sunscreen usage in humans. There have never been any reports of systemic side effects from oxybenzone and it has been on the market since 1978.
Retinyl palmitate is a derivative of vitamin A. It is commonly used to fortify milk, cereal and other food products. Concern has been raised that the use of retinyl palmitate might cause the production of free radicals following ultraviolet A exposure. The free radicals could possibly damage skin cells. Retinyl palmitate in sunscreens is used as an antioxidant and also to improve the cosmetic acceptability of sunscreens. There is no scientific evidence whatsoever of detrimental effects and it has actually been used to prevent skin cancer in high risk patients. Furthermore, when vitamin A is ingested orally via the diet, it is stored in our bodies as retinyl palmitate.
The most recent challenge to sunscreen safety is the presence of nanoparticles present in zinc oxide and titanium dioxide. When first rubbed onto the skin, these sunscreens look opaque white. They quickly break down into nanoparticles which makes them not only translucent but more effective. Concern has been raised that these products may release harmful reactive oxygen species. Because nanoparticles cannot pass through the stratum corneum, which is the uppermost layer of skin, systemic absorption is prevented or extremely limited.
We have all had exposure to nanoparticles via multiple other products for years. Research into both beneficial as well as harmful effects is ongoing. Until the effects of nanoparticles on the lungs has been further studied, it is advisable to avoid inhalation of spray sunscreens.
Perhaps the biggest controversy about sunscreens is the effect on vitamin D levels. Vitamin D is essential for strong bones and a healthy immune system. Thirty percent of the U.S. population is vitamin D deficient although controversy regarding exactly what level of vitamin D is considered normal.
In addition to diet, vitamin D is produced in the skin by sun exposure. When a sunscreen is used, less vitamin D is made in the skin. There is concern that lower vitamin D levels may result in bone fractures and internal cancers. That bone fractures can result from vitamin D deficiency is well established. Whether vitamin D deficiency can lead to cancer has been the subject of very heated debate with both sides citing medical studies in defense of their positions.
The National Institutes of Health (NIH) found no increase in cancer in patients with low vitamin D levels. The well-known Framingham Heart Study actually showed increased mortality with elevated vitamin D levels. The American Academy of Dermatology believes that it is foolish to expose yourself to ultraviolet light - a known carcinogen - when adequate vitamin D levels can be obtained through diet. Stay tuned to this issue. It is long away from being resolved.
So....... which sunscreen should you use? An effective sunscreen must block out both ultraviolet B rays (the burning rays) and ultraviolet A rays which do not cause a burn but penetrate more deeply. The ability to block ultraviolet B (not ultraviolet A) is measured by the SPF (sun protection factor). Choose an SPF of 30 or greater. The FDA is in the process of changing labeling for sunscreens because high SPF numbers can be misleading. For instance, an SPF of 50 blocks 98% of ultraviolet B rays. An SPF of 100 blocks 99% - essentially no difference.
To block the ultraviolet A rays - again, they do not burn but cause cancer and wrinkled skin - you should look for what is termed a broad spectrum sunscreen. The FDA is in the process of defining exactly how to use this term but you should look for one or more of the following ingredients:
Parsol 1789 (avobenzone)
Additional FDA labeling changes include discontinuation of the following terms: sunblock, all day protection, waterproof and sweat proof. Look for new definitions such as water resistant - 40 minutes and water resistant - 80 minutes.
- SPF 30 or higher
- Broad spectrum
- Apply enough
Remember that covering your entire body with sunscreen requires 2 tablespoons which is similar to the volume of a shot glass or the size of a golf ball. Also, remember to reapply sunscreens as needed.
ENJOY THE SUN BUT BE SMART ABOUT IT.
For more information, visit our website.