The American Academy of Dermatology also provides extensive information at its Web site. In evaluating the information from both sides, it's helpful to understand how tanning beds work. The radiation is emitted from tubular bulbs in the machine that surround the user, who lies inside the clamshell-like tanning bed. According to medical textbooks, UVB primarily affects the outer layer of the skin, while UVA penetrates deeper. Both, however, stimulate the production of the skin pigment melanin.
Melanin is manufactured to protect skin from the ultraviolet rays in sunlight.
It's also what makes moles look brown and gives people with darker skin their color. It's at this point that the views of the doctors and the industry begin to diverge. Mich. Many salons and manufacturers say the radiation emitted by bulbs is less harmful than natural sunlight. Dermatologists take issue with the industry's information. At the heart of the doctors' argument is the position that no tan is a good tan.