Tanning is the body’s natural response to ultraviolet light. The tanning process involves the relatively quick reddening of the skin followed by a slower forming, but longer lasting browning of the skin. The key is providing sufficient amounts of UVB to properly stimulate melanin followed with effective amounts of UVA to complete the tanning process.
UVA: The “tanning rays which have the longest wavelength and penetrate deepest into the skin.
UVB: The shorter wavelength rays that produce melanin which starts the tanning process.
Oxygen: Found in the bloodstream, it is brought to the surface of the skin and allows for the exudation or browning of the skin. Without oxygen, the tanning process could not take place.
Tanning occurs in the top layer of the skin, known as the epidermis. The outer layer of the epidermis, the horny layer, is made up of about 95 percent keratinocytes, or protein keratin, and 5 percent melanocytes, or pigment cells. The melanocytes use the amino acid tyrosine to produce melanosomes. The melanosomes contain the protein pigment, melanin, which is ultimately responsible for the tan one attains.
Everyone has the same number of melanocytes in their skin, but the amount of melanin your melanocytes will produce will be a function of each person’s genetic makeup, as well as their exposure to certain levels of ultraviolet light. Hence, heredity will ultimately determine your skin color and the capability of your skin to tan. Therefore it is imperative for tanning facilities to correctly identify the skin type of their clients to determine the proper exposure time, or whether tanning is appropriate at all.
Ultraviolet light is responsible for the tanning process which takes place in the skin. Ultraviolet light is that part of the electromagnetic spectrum from 200nm through 400nm. This part of the spectrum is further divided into three parts, UVC (200-280nm), UVB (280-320nm), and UVA (320-400nm). (Note: The definitions of UVB and UVC are slightly different in Europe than that defined by the FDA in the U.S. This accounts for different UVB% ratios for the same lamps in different parts of the world).
UVC is very destructive and is not part of the tanning process. The earth’s atmosphere blocks harmful UVC, hence acting to filter this radiation. In the case of fluorescent tanning bulbs, the glass acts to filter out these wavelengths.
UVB and UVA both exist in natural sunlight and in tanning bulbs. They are also both critical in the tanning process. The UVB stimulates melanin production which results in more pigment cells and a consequent thickening of the skin. This latter process, known as hyperplasia, is important in protecting the skin from further exposure. The UVA oxidizes the melanin, with a browning or tanning effect.
Ultimately, the tanner’s skin type will determine the range of tan one can get. The bulbs one uses and the amount of exposure to those bulbs will determine the type of tan within that range.
Understanding this process helps us to understand that both UVA and UVB are important in the tanning process. As a result, the amount of UVA and UVB coupled with the tanner’s genetic makeup will determine the color and depth of tan.