The sunless tanner dihydroxyacetone (DHA) is currently the most popular way of gaining a tan without sun exposure. It carries less health risks than any of the other available methods. To date, it is the only active ingredient approved by the US Food & Drug Administration (FDA) for sunless tanning.

The skin is made up of two main layers: the epidermis on the outside and the dermis on the inside. Whether you are talking about sun tanning or self-tanning, the epidermis is where the action occurs. The epidermis is also made up of layers. The deepest layer of the epidermis, called the stratum basale (basal layer), is affected during sun tanning. The stratum corneum (horny layer) is the outermost layer of the epidermis -- it is this layer that is affected by most sunless-tanning products.

There are several different kinds of sunless-tanning products available today. People have been able to pour on a tan since 1960, when Coppertone® came out with the first sunless-tanning product -- QT® or Quick Tanning Lotion. If you are old enough to remember this, then you are probably thinking of the incredibly orange hue this lotion produced. Since then, there have been several advancements made on the sunless-tanning front. These days, you can find tanning pills, sunless- or self-tanners and bronzers. You can smooth, swipe or spray on a light bronze glow or a deep, dark tan.

According to the American Academy of Dermatology, the most effective products available are sunless or self-tanning lotions that contain dihydroxyacetone (DHA) as the active ingredient. DHA is a colorless sugar that interacts with the dead cells located in the stratum corneum of the epidermis. As the sugar interacts with the dead skin cells, a color change occurs. This change usually lasts about five to seven days from the initial application.

DHA has been used in cosmetic preparations for almost 30 years and was listed with the FDA in 1973. In addition to its skin darkening abilities, DHA is also used as an emulsifier, humectant and fungicide. It is declared safe and suitable for use in cosmetics and drugs used to color the skin. DHA is derived from glycerin (vegetable origin), which is a commonly used cosmetic and food ingredient. DHA is not absorbed into the body and poses no possibility of toxicity.

Every day, millions of dead skin cells are sloughed off or worn away from the surface of your skin. In fact, every 35 to 45 days, you have an entirely new epidermis. This is why tans from sunless- or self-tanning lotions will gradually fade -- as the dead cells are worn away, so is your tan. For this reason, most of these products suggest that you reapply the sunless or self-tanner every week or two to maintain your tan.