Sunscreens and cancer
Sunscreens are topical products designed to protect the skin from the sun's harmful ultraviolet (UV) rays, which are known to cause sunburn and increase the risk of skin cancer. They work by incorporating a mix of organic and inorganic ingredients, such as avobenzone, oxybenzone, zinc oxide, and titanium dioxide, that absorb, reflect, or scatter UV radiation. Sunscreens are classified based on their Sun Protection Factor (SPF), which indicates the level of protection they provide; a higher SPF typically means better protection against sun damage. The American Academy of Dermatology recommends using a broad-spectrum sunscreen with at least SPF 30 for effective skin cancer prevention.
To maximize effectiveness, sunscreen should be applied 15 to 30 minutes before sun exposure and reapplied every two to three hours, especially after swimming or sweating. It's important to note that most people do not apply enough sunscreen, and proper application is crucial for optimal protection. Additionally, while sunscreens play a significant role in reducing skin cancer risks, they should be part of a comprehensive sun safety program that includes seeking shade, wearing protective clothing, and avoiding peak sun hours. Despite their benefits, some individuals may experience mild allergic reactions to specific ingredients in sunscreens, which can often be resolved by switching products.
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Subject Terms
Sunscreens and cancer
ALSO KNOWN AS: Avobenzone, oxybenzone, ecamsule, zinc oxide, titanium dioxide
DEFINITION: Sunscreens are lotions or sprays that, when applied correctly, can help prevent sunburn and other kinds of skin damage from the sun’s ultraviolet (UV) rays. Using sunscreen can lower a person’s risk for skin cancer.
Cancers treated or prevented: Skin cancers
Delivery routes: Topical via lotions and creams
How these agents work: There are two types of UV light from the sun, UVA and UVB. UVA rays damage the skin with long-term effects such as premature wrinkles and skin aging because they penetrate deep into the skin. UVB radiation causes sunburns and most likely contributes to skin cancers. Most sunscreens do not block UVA as well as they do UVB rays. It is recommended that a broad-spectrum sunscreen be used to protect against both types of UV radiation.
Sunscreens contain both organic and inorganic ingredients such as avobenzone, oxybenzone, zinc oxide, and titanium dioxide. They work by absorbing, reflecting, or scattering UVA and UVB rays from the sun. Most sunscreens contain a combination of these ingredients, which work together to have a synergistic effect in protecting the skin. In 2006, the US Food and Drug Administration approved a form of ecamsule (Meroxyl, Tinosorb) for use in limited products but not yet for widespread use in the United States. Used in Canada and Europe, ecamsule is more photostable than other ingredients and retains its stability when exposed to sunlight. It remained only available in a handful of products in the US in the mid-2020s. More effective ingredients in sunscreens that offer increased sun protection are available in Asian and European countries. However, because of rules on how these chemicals must be tested for commercial use, they are not available to US consumers.
Sunscreens have a sun protection factor (SPF) number that refers to how long the sunscreen is effective on the skin. The higher the SPF, the more sun protection the sunscreen offers. This number is only an estimate, however, because many additional factors, such as how much and how often the sunscreen is applied, how much sunscreen is absorbed, and the person’s activity (for example, sleeping in the sun, swimming, or exercising) affect how the sunscreen works. The FDA recommends a minimum SPF of 15, while the American Academy of Dermatology recommends a minimum SPF of at least 30. Higher numbers of SPF exist, but with consistent reapplication, SPF 30 remains most recommended by doctors. SPF protection, however, can reach as high as 60 and 80 SPF.
Sunscreen works best when applied fifteen to thirty minutes before sun exposure, followed by a reapplication fifteen to thirty minutes after being out in the sun. Sunscreen then needs to be applied every two to three hours to remain effective on dry skin; after forty minutes of swimming or sweating, sunscreen should be applied immediately to towel-dried skin. Most people do not apply enough sunscreen. Studies have shown that one ounce or two tablespoons is needed to cover the average body adequately.
In December 2012, the FDA released new guidelines regarding the information shown on sunscreen labels. The new labels show whether the sunscreen is broad spectrum, has an SPF of 15 or higher, includes a skin cancer/skin aging alert, and is water-resistant (for forty minutes or eighty minutes). For products that are not broad spectrum or are broad spectrum but have an SPF of 2 to 14, the label must state that the product has been proven to help prevent sunburn but not skin cancer or early skin aging. Furthermore, the labels must include updated directions for how frequently water-resistant and non-water-resistant products should be applied to be effective. The FDA guidelines also prohibit labels from using the misleading terms, such as sunblock, sweatproof, waterproof, all-day or other extended wear claims, and instant protection.
No matter what sunscreen is used, some UV radiation still gets through to the skin. A total program is needed to decrease the sun’s harmful effects:
- Use a broad-spectrum, water-resistant sunscreen with an SPF of 30 or higher every day, even on cloudy days
- Avoid the sun during the hours of 10:00 A.M. to 4:00 P.M.
- Wear a hat, sunglasses, and long-sleeved protective clothing when out in the sun
- Reapply sunscreen at least every two hours or more to dry skin; after swimming or sweating for forty minutes, reapply sunscreen immediately after toweling off
Side effects: Occasionally, some people develop a mild to moderate allergic reaction or rash in reaction to some of the active ingredients in sunscreens. Discontinuing that sunscreen and switching to another type usually corrects this problem.
Bibliography
“Ecamsule.” PubChem, pubchem.ncbi.nlm.nih.gov/compound/Ecamsule. Accessed 23 June 2024.
“Labeling and Effectiveness Testing: Sunscreen Drug Products for Over-T.” FDA, 17 Dec. 2012, www.fda.gov/regulatory-information/search-fda-guidance-documents/labeling-and-effectiveness-testing-sunscreen-drug-products-over-counter-human-use-small-entity. Accessed 23 June 2024.
Scaturro, Michael. “What's Keeping the U.S. from Allowing Sunscreens with Better UV Ray Protection.” NBC News, 4 May 2024, www.nbcnews.com/health/health-news/us-sunscreen-fda-ingredients-uv-protection-rcna150307. Accessed 23 June 2024.
“Sun Protection.” MedlinePlus, 7 June 2023, medlineplus.gov/ency/patientinstructions/000378.htm. Accessed 23 June 2024.
“Sunscreen FAQs.” American Academy of Dermatology, 15 Apr. 2024, www.aad.org/media/stats-sunscreen. Accessed 23 June 2024.
“Sunscreen: How to Help Protect Your Skin from the Sun.” FDA, 17 May 2024, www.fda.gov/drugs/understanding-over-counter-medicines/sunscreen-how-help-protect-your-skin-sun. Accessed 23 June 2024.