New trends in sunscreen testing and labeling

In December 2012, the U.S. Food and Drug Administration enacted labeling rules to help remedy consumer misperceptions about sunscreen.The Academy recently discussed new developments in sunscreen labeling with Joseph Stanfield,an AAD affiliate member and president of Suncare Research Laboratories, a testing laboratory that specializes in measurement of sun protection.

AAD: There is no question that most skin cancers are related to sun exposure, yet even with sunscreen sales approaching $1 billion a year, skin cancer rates continue to climb. How will this new labeling help educate the public about sun safety?

Mr. Stanfield: Until recently, many sunscreens with a high sun protection factor (SPF) were designed primarily to protect people from ultraviolet B (UVB) rays, the main cause of sunburn. These sunscreens may have enabled users to stay out longer but did not necessarily protect them from ultraviolet A (UVA) rays. Use of the label “broad-spectrum protection” now means the sunscreen has been proven to protect against UVA and UVB rays.

What many people don’t realize is the protection you get isn’t proportional to the SPF numbers.

This is an important development because it draws public attention to the role UVA (long-wave energy)  plays in sun damage and skin cancer. It was once thought that only UVB (short-wave energy) were of concern. However, multiple studies over the past two decades show that UVA contributes significantly to skin damage.

AAD: The FDA’s Sunscreen Labeling Protection Act allows sunscreens that meet the criteria for both “broad spectrum” labeling and have an SPF of 15 or greater to claim that “…used as directed with other sun protection measures these sunscreens reduce the risk of skin cancer and premature skin aging.” However, the FDA has requested  additional data before permitting SPF values above 50+.  Why?

Mr. Stanfield: The FDA does not have adequate data demonstrating that products with SPF values higher than 50 provide additional protection compared to products with SPF values of 50. They will rule on the use of SPF values above 50+ at sometime in the future.

Many people think that the protection you get isn’t proportional to the SPF numbers. An  SPF 15 blocks 93.3% of the solar energy; while an SPF 30 blocks 96.7%. This appears to be a small difference in protection, however, it’s the transmitted energy that matters. An SPF 15 allows 6.7% of the solar energy to reach the skin, while an SPF 30 transmits 3.3 percent, and an SPF 50 transmits 2 percent. Most dermatologists agree that SPF 30 is sufficient, based on the total amount of solar energy in a typical summer day. However, a recent paper in JAAD (2013:69; 867-80) showed that SPF values of 70 and higher can provide a safety factor when the amount of sunscreen applied is slightly lower than the recommended amount, or partially rubbed off. The amount applied in the SPF test corresponds to 40 grams for the whole body (2 mg/cm2). For convenience, a new recommended mnenomic for the recommended amount is based on the “teaspoon rule”, which is 1 teaspoon to the head/face/neck, 1 teaspoon to each arm, 1 teaspoon to the front torso, 1 teaspoons to the back torso and 2 teaspoons to each leg. You will recognize a slight variation in the familiar “Rule of Nines”. JAAD (2013;69:867-80.)

In addition, the FDA rule prohibits labeling terms like ”waterproof” (”40 minute water-resistant” or  “80 minute water resistant” allowed),”sweatproof” and “all day protection.”

                Sunscreen timeline

AAD:  How does your laboratory evaluate the effectiveness of a sunscreen?

Mr. Stanfield: Typically, the SPF is measured on human volunteers by applying 2 mg/cm2 of a sunscreen formula to an area of the mid-back, allowing the sunscreen to dry for 15 minutes, and administering a series of five increasing doses of ultraviolet energy (UVR), simulating sunlight, to skin sites treated with the sunscreen.

Another series of five increasing UVR doses is applied within a skin area without the sunscreen. After 16 to 24 hours, the irradiated skin sites are examined to determine the SPF. The SPF is the lowest dose of UVR that caused mild sunburn with clearly defined borders (the minimal erythema dose, or MED) in the sunscreen-treated area divided by the MED  in the area without sunscreen. The label SPF of a sunscreen formula is based on the average SPF for 10 volunteers.

Dr. Steven Feldman, who directs the Center for Dermatology Research and is a professor of dermatology at Wake Forest University, serves as our consultant. He serves as our investigator in safety studies and provides medical input, as needed.

There are also other methods of measurement that don’t rely on human subjects under development, because UVR is a carcinogen. Current non-invasive methods for measurement of sunscreen SPF include in vitro measurements on artificial substrates that simulate the skin surface, and computerized mathematical models based on the UVR absorbance spectra of active ingredients. The latter approach is known as “in silico” measurements, owing to the fact that computers are composed of silicon circuit components. These measurements present formidable challenges for a variety of reasons. However,we and other laboratories, world-wide, are pursuing approaches to meet these challenges.

Joseph Stanfield is president of Suncare Research Laboratories in Winston Salem, N.C. His career in sunscreen research spans more than 30 years, beginning with Bristol Myers Squibb, as manager of photo biology research. He was also responsible for sunscreen testing and sensory evaluation at Schering-Plough (now Merck), before founding Suncare Research Laboratories in 1999. He has a master’s degree in aerospace engineering from Auburn University, with coursework in physiology and biotechnology. His research interests include mathematical modeling of biological systems and innovative applications of image analysis. He is author or co-author of more than 70 scientific publications.

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