What is sunless tanning?

Self-tan products help you develop a natural looking tan without the sun. If you've ever seen a sliced apple turn from white to brown, you've seen how self-tan products work on your skin. Natural chemicals cause the inside of the apple to turn brown when it's exposed to air. The naturally occurring chemical dihydroxyacetone, commonly known as DHA, does the same thing to your skin. DHA is the main ingredient in self-tan products.

Is DHA safe? 

DHA is a colorless sugar derived from plants such as sugar beets and sugar cane. It has been used to treat medical problems such as skin-pigmentation disorders for more than 50 years. In the 1970s it was added permanently to the United States Food and Drug Administration (FDA) list of approved cosmetic ingredients [source: FDA].

DHA has an enzymatic reaction with the amino acids in the outer layer, or epidermis (stratum corneum), of the skin, causing the dead skin cells to turn temporarily darken, producing a golden brown tan colour. Just as it takes the apple a while to turn brown, so can it take several hours for the DHA to darken your skin. Thus most self-tanners recommend leaving the application on for 4-6 hours before washing it off in the shower. During this time, the DHA would react with the skin to produce the tan colour. The skin would be left looking golden and bronzed when the application is washed off in the shower after 4-6 hours.

The effects of the DHA are temporary. You are constantly shedding dead skin cells, so within a few days, this "tan" will be gone. The tan lasts about 7-10 days depending on your skin type and how well you moisturise after. Most products advise a new application weekly to keep a "tan" current.

Why not just tan under the sun?

By contrast, going under the sun to get a tan involves UV rays penetrating into the deepest layers of your skin. That's why it cause lasting skin damage.

Sunlight is made up of several types of rays—ultraviolet B (UVB), ultraviolet A (UVA), and ultraviolet C (UVC). While UVB rays are responsible for suntans or burns, it's the subtle UVA rays that cause wrinkles and fine lines. Either way, exposure to every kind of ultraviolet light is the root cause of all skin cancer.

By weakening the body's immune system and harming healthy DNA, UV rays are a direct cause of skin cancer, as well as freckles, moles, wrinkles and fine lines, and results are cumulative. The more time spent in the sun, the more your skin's ability to defend itself diminishes.

With every passing year, signs of damage caused by the sun—known as photo aging—will emerge on the skin. Skin will appear thinner and more fragile, freckles and moles will darken, the texture may become tough or leathery and wrinkles will crease and deepen as the collagen and elastin breakdown even further. When UV rays break down the collagen structure, it results in wrinkles. Once collagen is damaged, it cannot re-build itself. This process with hasten with more time spend under the sun.

The sun causes up to 80% of premature aging, making sun protection one of the best defenses against wrinkles. The more you protect your skin from sun exposure in the first place, the less time — and money — you will spend trying to "cover up" the damage in the future.

Generally speaking, most dermatologists consider self-tanning to achieve that “sun-kissed glow” much safer than obtaining a tan from the cancer-causing ultraviolet (UV) radiation that comes from the sun or tanning booths. The European Commission's Scientific Committee on Consumer Safety has issued a comprehensive Opinion on DHA in which after considerable review concluded that spray tanning with DHA solutions did not pose risk to the consumer [source: European Union].