Myth: Sunscreens cause cancer
Regular sunscreen use is recommended by the American Academy of Dermatology as a primary method of sun protection to reduce the risk of melanoma and other nonmelanoma skin cancers. However, due to reports in the media, patients often inquire if sunscreen ingredients, specifically oxybenzone and retinyl palmitate as well as nanoparticles, are toxic and actually cause malignant melanoma and other skin cancers rather than prevent them.
Overall, the known benefits of sunscreen use to minimize short-term and long-term damage to the skin from UV radiation outweigh any unproven claims of toxicity or human health hazard. Active ingredients in sunscreens, such as oxybenzone and retinyl palmitate, are regulated as over-the-counter drugs by the US Food and Drug Administration and have a long-standing history of providing effective broad-spectrum protection from UV radiation. Despite concerns that oxybenzone can penetrate the skin and effect hormone levels, there is no evidence supporting this claim. Although oxybenzone is absorbed by the body, it is subsequently excreted and has no potential for harmful buildup. It also has been suggested that retinyl palmitate generates free radicals that can lead to cancer formation; however, the risk has only been linked to UV exposure in isolation, and antioxidants in the body can theoretically neutralize these free radicals before they lead to cancer development.
Sunscreens containing nanoparticles of inorganic filters such as zinc oxide and titanium dioxide also have been scrutinized. These formulations have largely proven effective in protecting against UVA and UVB radiation, and claims that nanoparticles are small enough to penetrate the epidermis and be absorbed in the human bloodstream have been refuted.
The positive association between sunscreen use and risk of developing malignant melanoma may be due to selection bias and uncontrolled confounding in studies rather than proven toxicity of sunscreen ingredients. Results from a meta-analysis of 11 case-control studies indicated that there is no association and the researchers discussed the role of selection bias in contributing to the positive association between sunscreen use and melanoma development. For instance, some studies failed to control for factors that commonly are linked with increased melanoma risk (eg, red or fair hair color, blue eye color, presence of nevi, freckling). Also, increased sun exposure among patients who use sunscreens may have impacted study results.
Dermatologists should emphasize to concerned patients that long-term sunscreen use has been proven to reduce the incidence of melanoma. A 2011 Australian study evaluated the effects of long-term application of sunscreen on the risk of cutaneous melanoma in 1621 randomly selected participants who applied sunscreen in combination with 30 mg of beta-carotene or placebo supplements for 4 years and were observed for 10 more years. They observed a reduction in primary melanomas and invasive melanomas in the sunscreen group, concluding that melanoma may be preventable with regular sunscreen use in adults.
For patients who are still concerned, dermatologists can recommend sunscreens containing organic UV filters only. Education about factors that contribute to the increased rate of melanoma also is necessary. Longer lifespans, the thinning ozone layer, increased popularity of outdoor activities, exposed skin due to clothing style, use of tanning beds, earlier detection of skin cancer, and other factors may be responsible. Greater exposure to UV radiation rather than commercial sunscreens is the likely cause of skin cancer.