From Anne Marie Helmenstine, Ph.D.,
Your Guide to Chemistry.
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A. Self-tanning products have been around in some form or other since the invention of cosmetics. In 1960, Coppertone introduced its first sunless tanning product - QT® or Quick Tanning Lotion. This lotion produced an overall orange effect. Today's sunless tanning products produce much more realistic results. Tanning pills, sunless-tanning or self-tanning lotions and sprays, and cosmetic bronzers are available to impart a subtle bronze glow or a deep, dark tan. Bronzers yield immediate results, although some sunless tanning products require 45 minutes to an hour before taking effect. Although sunless tanning products can yield a golden glow, they do not protect the skin from the ultraviolet radiation in the sun's rays the way melanin in a 'real' tan does, so users of sunless tanning products need to apply sunscreen before venturing out in the sun.

Tanning on the Outside

• Bronzers
  Cosmetic bronzers produce immediate effects that can be easily removed with soap and water. Bronzers are available as powders, creams, and lotions. These products are essentially a form of make-up, since the tint only lasts until it is washed off.

• Tanning Lotions and Sprays
  Perhaps the most effective sunless tanning products are lotions and sprays containing dihydroxyacetone (DHA) as the active ingredient. DHA is a colorless sugar that interacts with the dead cells located in the upper layer of the epidermis. As the sugar interacts with the dead skin cells, a color change occurs. This change usually lasts about five to seven days from the initial application.

Tanning from the Inside

• Tanning Pills
  Tanning pills typically contain the pigment canthaxanthin. Although the FDA has approved the use of canthaxanthin as a color additive in food, it has not approved its use as a tanning agent. Much larger quantities of canthaxanthin than the amount used as a food coloring must be ingested to change skin color. After canthaxanthin is consumed, it is deposited throughout the body, including in the skin, which turns an orange-brown color, and also the internal organs (liver, brain, etc.). Canthaxanthin-based tanning pills have been linked to dangerous side effects, including hepatitis (inflammation of the liver) and canthaxanthin retinopathy (formation of yellow deposits in the retina of the eye).

• Tanning Accelerators
  Most tanning accelerators are lotions or pills that contain the amino acid tyrosine. Makers of these products believe that the tyrosine stimulates and increases melanin formation, thereby accelerating the natural tanning process. However, more scientific data is needed to determine the validity of these claims and to assess the safety of using large amounts of tyrosine.

Why Do Tans Fade?

Skin takes a lot of wear and tear, so it naturally regenerates itself. Every 35-45 days the outer layer of the skin, the epidermis, is completely replaced. Since skin pigment is found in this upper layer, any natural or added pigment will be sloughed away in about one month's time. This is why natural tans fade and why many self-tanning products recommend you re-apply the product every few days to maintain your tan.