Natural tanning facts
Let's talk about it in words simple to understand. The 'tan' is actually a colored pigment in the skin which protects the skin from excessive UV radiation. Ultraviolet (UV) rays are part of a vast spectrum of rays emitted by the sun. More the exposure to UV rays, more is the pigment produced by the skin glands.
The outer layer of the skin, called epidermis, contains three kinds of special cells. The one that concerns us, and what we are talking about now, is the melanocytes.
Melanocytes are the cells that produce the colored pigment - melanin - which makes the skin look 'tanned'. The amount of naturally produced melanin varies from race to race as it depends wholly on heredity. African-Americans have high amounts of melanin which makes their skin look black or dark brown. Caucasians have much lesser melanin which makes their skin look light.
Indoor tanning beds
The indoor tanning bed simulates the emission of UV rays. Special lamps in the equipment emit a controlled amount of UV rays according to specific needs of tanning. The skin responds by producing melanin, thus giving you a tan. Since the radiation is carefully controlled, indoor tanning is considered safer than tanning out in the sun.
UV rays, if further broken down for analysis, consist of UVA, UVB and UVC rays. UVC rays never reach us as they are blocked by the ozone layer. Of the remainder, UVA make up for 95% and UVB 5%. They each have their specific roles which you can find out if interested. The tanning beds have control over these specific rays and that makes them a better bet than the beach.
Sunless tanning products
Some of these products go straight to the melanocytes and get them to produce more melanin, or so they claim. Many products contain dihydroxyacetone which is a colorless sugar that interacts with dead cells of the epidermis and thereby changes color. This change lasts for five to seven days. Other products like tanning pills produce the pigment canthaxanthin throughout the body including the skin, which gives it the orange brown color. But mind you, some of these chemicals may be harmful. Always lay your hands on all the information you can.