What are sunscreens? Do they help prevent 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 a single sunscreen product but not yet for widespread use in the United States. Used in Canada and Europe, ecamsule has proven to be more photostable than other ingredients and therefore retains its stability when exposed to sunlight.

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 recommended a minimum SPF of 15 in 2012, while in 2014 the American Academy of Dermatology recommended a minimum SPF of at least 30.

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 new FDA guidelines regarding the information shown on sunscreen labels. The new labels show whether or not 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 in order to be effective. The FDA guidelines also prohibit labels from using the misleading terms sunblock, sweatproof, waterproof, all-day or other extended wear claims, and instant protection.

In reality, 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

AHFS Consumer Medication Information, Amer. Soc. of Health-System Pharmacists. "Sunscreens." MedlinePlus. US NLM/NIH, 15 Aug. 2011. Web. 4 Nov. 2014.

Amer. Acad. of Dermatology. "Sunscreen FAQs." AAD.org. AAD, 2014. Web. 4 Nov. 2014.

US Food and Drug Admin. "CFR—Code of Federal Regulations Title 21, Volume 5 [21CFR352.10]." Accessdata.FDA.gov. US FDA, 1 Apr. 2014. Web. 4 Nov. 2014.

US Food and Drug Admin. "CFR—Code of Federal Regulations Title 21, Volume 5 [21CFR352.20]." Accessdata.FDA.gov. US FDA, 1 Apr. 2014. Web. 4 Nov. 2014.

US Food and Drug Admin. "FDA Approves a New Over-the-Counter Sunscreen Product." FDA.gov. US FDA, 24 July 2006. Web. 4 Nov. 2014.

US Food and Drug Admin. "FDA Sheds Light on Sunscreens." FDA.gov. US FDA, 20 Aug. 2013. Web. 4 Nov. 2014.

US Food and Drug Admin. "Labeling and Effectiveness Testing: Sunscreen Drug Products for Over-the-Counter Human Use—Small Entity Compliance Guide." FDA.gov. Dec. 2012. US FDA, 13 May 2014.

US Gov. Printing Office. "Labelling and Effectiveness Testing; Sunscreen Drug Products for Over-the-Counter Human Use; Delay of Compliance Dates." Federal Register 77.92 (2012): 27591–27593. Digital file.