Sunscreen and Sun Protection Update
Clinical Professor of Dermatology
University of Iowa School of Medicine
Des Moines, IA
Sunscreens are frequently in the news and social media for a variety of reasons, and patients often have questions ranging from the safety of ingredients to optimal usage. In this session, Roger Ceilley, MD provided a very helpful update on sunscreen and skin cancer prevention. Dr. Ceilley began by sharing data on how sunscreen usage can reduce the risk of melanoma. In a large study of 1,621 residents of Australia, people were randomly assigned to daily or discretionary sunscreen usage on the head and arms for 5 years, and then followed for 10 years. At the end of that period, subjects who were assigned to daily sunscreen usage had a 0.27 relative risk of developing invasive melanoma compared to those who used sunscreen at their own discretion.
Next, Dr. Ceilley discussed various SPF levels and how much is really enough. With regard to UVB absorption, there is only a marginal increase of 1% when switching from SPF 100 to SPF 50. However, this assumes sunscreen is being applied at the tested concentrations of 2 mg/cm2, when in reality patients typically apply about 25-50% of this amount. In a real world randomized, double-blind, split-face, natural sunlight exposure clinical trial that was published in the JAAD, the investigators found that the half of the face with SPF 50 on it was 11 times more likely to be sunburned then the half of the face with SPF 100 on it.
Dr. Ceilley concluded by discussing environmental concerns that have been attributed to sunscreen. The majority of sunscreens contain oxybenzone, and in laboratory studies of oxybenzone at significantly increased concentrations suggested that it could have a negative environmental effect. However, these experiments were not reflective of real-world concentrations of oxybenzone in sunscreen and therefore the results are inconclusive. Additionally, people often worry about the risk of systemic absorption of oxybenzone or benzene and the potential for this to cause cancer. Dr. Ceilley pointed to an analysis of data from the National Health and Nutrition Examination Survey for 10,861 adults that found sunscreen users were actually less likely to have elevated levels of benzene than never users. This suggests that risk of systemic benzene exposure from sunscreen use may be low and likely due to other factors such as exposure to gasoline emissions, cigarette smoke, and occupational chemicals.