Tanning beds have long been utilized by those who desire a year 'round tan that takes less time to acquire than lying in the sun. Tanning beds work by creating an artificial sources of ultraviolet light, which is present in two forms: ultraviolet-A (UVA) light or ultraviolet-B (UVB) light. Each form of ultraviolet light has an impact on the skin in different ways, and tanning beds are available in UVA, UVB or a combination of both light wavelength options.
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UVA Tanning Beds
UVA rays are longer than their UVB counterparts and penetrate the skin's epidermis, which is composed of five layers. UVA rays penetrate more deeply than UVB rays, reaching the lower layers of the epidermis, which are known as the stratum spinosum and the stratum basale. When the rays of a UVA tanning bed hit a person's skin, they penetrate and cause the skin to produce melanocytes. These melanocytes produce melanin--a brown pigment that causes people to appear tan. The more melanin produced, the more tan a person appears.
UVB Tanning Beds
UVB tanning beds utilize UVB rays, which are shorter than UVA rays. This means the rays penetrate less deeply into the skin, typically affecting the outer layers of the epidermis. When overexposed to UVB rays, a sunburn can occur, as the rays can cause the capillaries below the skin's surface to pop, creating a red, raw appearance. UVB rays are generally regarded as the chief contributors to skin cancers, such as melanoma or squamous cell carcinoma, according to kidshealth.org. Most tanning beds, however, emit less UVB rays than the sun, according to Vanderbilt University.
When evaluating a UVA versus UVB tanning bed in terms of damaging effects, there are trade-offs associated with each type. UVB rays are associated with more serious health effects, such as skin cancers while UVA rays are associated with skin damage--including wrinkling, age spots and fine lines.
Combination Tanning Beds
Most tanning beds contain some combination of UVA and UVB wavelengths in order for the user to achieve a tan. The reason for this is that UVA rays are associated with appearing more tan; however, UVB rays also are responsible for bringing melanin to the surface, which can make a person appear more tan. When present in combination, tanning bed lamps typically emit 93 to almost 99 percent UVA rays and 7 to 1 percent UVB rays.
The reason why UVA and UVB rays cause a person to tan much faster than when a person is exposed to the sun is chiefly due to proximity. While the sun is millions of miles away, the ultraviolet light (UVA, UVB or other) given off by a tanning bed is much closer to a person's skin, which can speed the tanning process significantly.