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    How does sunscreen work?


    By combining organic and inorganic active     ingredients.

Sunscreen works by combining organic and inorganic active ingredients. Inorganic ingredients like zinc oxide or titanium oxide reflect or scatter ultraviolet (UV) radiation. Organic ingredients like octyl methoxycinnamate (OMC) or oxybenzone absorb UV radiation, dissipating it as heat. Some sunscreens protect us from the two types of damaging UV radiation: UV-A and UV-B. Both UV-A and UV-B cause sunburns and damaging effects such as skin cancer.

Ultraviolet radiation is broken into three types of wavelengths:

  • UV-A: This is the longest wavelength and is not absorbed by the ozone. It penetrates the skin deeper than UV-B.
  • UV-B: Responsible for sunburns. It is partially blocked by the ozone layer.
  • UV-C: This is totally absorbed by the earth's atmosphere; we encounter it only from artificial radiation sources.

Bottle of sunscreenWhen purchasing sunscreen, the Sun Protection Factor or SPF measures how effectively the sunscreen formula limits skin exposure to UV-B rays that burn the skin. The higher the SPF the more protection the sunscreen will provide against UV-B rays. SPF does not measure UV-A. If you are looking for UV-A protection, the experts recommend that you purchase a product that has broad-spectrum protection.

Standard DisclaimerRelated Web Sites
  • Sunscreen: How to Select, Apply, and Use it Correctly - The Centers for Disease Control and Prevention provides a brief list of sunscreen recommendations.
  • American Academy of Dermatology External Link - The Sunscreen FAQS website gives information about choosing sunscreen, applying sunscreen, treating sunburns and other questions relating to protecting your skin from the sun.
  • FDA Aims to Upgrade Sunscreen Labeling - FDA wants the labeling on your sunscreen to tell you more about protection against the sun's harmful rays.
  • Sun Safety - A guide to the UV index and Sun-Safe Behavior. This website from the EPA provides information about UV, health risks of sun exposure, and how to protect yourself from the damaging effects of the sun.
  • Climate Prediction Center: Current UV Index Forecast - This website provides the UV index at high noon for the United States.
  • UV Radiation: NASA - NASA Advanced Supercomputing Division educational resource on ultraviolet radiation contains an introduction to ultraviolet radiation and the health effects of UV-B radiation. References are also cited at the end of the article.

Library of Congress Web SiteFurther Reading
  • Reisch, Marc. Sunscreens: active ingredients prevent skin damage. Chemical & engineering news, v. 80, June 24, 2002: 38. External Link
  • Sunscreens: development, evaluation, and regulatory aspects. Edited by Nicholas J. Lowe, Nadim A. Shaath, and Madhu A Pathak. 2nd ed. New York, Marcel Dekker, c1997. 792 p.
  • Sunscreen. In How products are made: an illustrated guide to product manufacturing. Edited by Jacqueline L. Longe. v.2. Detroit, Gale Research, c1996. p. 429-433. External Link
  • UV-B radiation and ozone depletion: effects on humans, animals, plants, microorganisms, and materials. Edited by Manfred Tevini. Boca Raton, FL, Lewis Publishers, c1993. 248 p.
  • United States. Adequacy of protection from sunglasses and sunscreens: hearing before the Ad Hoc Subcommittee on Consumer and Environmental Issues of the Committee on Governmental Affairs, United States Senate, One Hundred Second Congress, Second session, June 5, 1992. Washington, U.S. G.P.O., 1993. 294 p.

SearchFor more print resources...
Search on "sunscreen," "uv" and "ultraviolet" in the Library of Congress Online Catalog.

Photo: father applying sunscreen to daughter[Father applying sunscreen to his daughter]. From the Centers for Disease Control and Prevention website.

Photo:  women  at the beach, modeling summer beach attire .Society leaders display 200 years of beach attire at Cape May Sun Tan Cabana Club. Underwood and Underwood, 1931. Prints and Photographs Division, Library of Congress.

Adult applying  sunscreen to child
An adult applying sun screen on a child. From the Centers for Disease Control and Prevention website.

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 August 14, 2017
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