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The Facts About How Skin Tans

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Updated April 30, 2014

Many people want a tan, but do you know how skin tans? A great amount of money, time and effort goes into getting, and keeping, tanned skin. Our teens are often preoccupied with having a “perfect” and even tan. But how does it happen?

Ultraviolet Rays

Our sun produces three main types of ultraviolet rays: UVA, UVB and UVC. UVC rays are caught by our ozone layer and don't play a factor in tanning. Most, but not all, of UVB rays are also caught in the ozone layer, so some UVB rays play a factor in tanning. When we are talking about tanning by the sun's ultraviolet rays, UVA and some UVB rays are what causes the tan.

Ultraviolet rays are not created equally. UVA rays and UVB rays have different wavelengths, allowing the rays to penetrate different layers of the skin. UVB rays have short wavelengths and penetrate the outermost layers of the skin (the epidermis). UVA rays have longer wavelengths and can penetrate deeper than UVBs, right into the dermis, the middle layer of the skin.

How UV Rays Cause a Tan

UV rays cause tanning by the way they affect the melanin in our skin. Melanin is a pigment in our skin and is what gives our skin its color.

  • UVA causes a tan by oxidating the melanin. Essentially, the melanin undergoes a chemical reaction after being exposed to UVA, causing it to become darker. When the melanin looks darker, the skin itself looks tanned and dark.
  • UVB causes a tan in a different method. UVB causes an increase in production of melanin in the skin and other changes to the cells that the melanin is stored in. These UVB effects cause the skin to become darker or tanned.

What About Tanning Beds?

Tanning beds and tanning lights used to be thought to be a safe alternative to tanning outside, but those claims are absolutely not true. Older tanning beds used to produce UVB waves that caused more burning, so these beds were changed to use UVA waves. These waves don't burn the skin the same way that UVB waves burn, but that does not mean they are safe. UVA waves are thought to cause skin cancer and immune system issues. If you have ever seen someone who has tanned extensively throughout their lifetime, you can see that the UVA waves damage the skin in a way that promotes deep wrinkling.

UVA and UVB rays, from the sun or from a tanning bed, are what cause the skin to tan. There are risks to tanning, and it is important to discuss your concerns with your teen. It's what's best for their health.

Sources:

Behrman, RE, Kliegman, RM, and Jenson, HB. Nelson Textbook of Pediatrics, 2004.

Indoor Tanning. Federal Trade Commission. http://www.ftc.gov/bcp/edu/pubs/consumer/health/hea11.shtm. May 3, 2009.

Tanning. U.S. Food and Drug Administration. http://www.fda.gov/cdrh/tanning/uvradiation.html May 2, 2009.

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