Inside the sunless tanning booth can be up to 36 spray heads each connected to a compressor unit. These heads can be either fixed or tuned to move in a motion that best evenly covers the skin with the tanning solution. Companies all seem to utilise different technologies when it comes to administering the tan. Some have opted to increase the number of heads and keep them fixed; arguing that moveable head systems require constant maintenance thus increasing the risk of a tanning catastrophe! In some salons clients are instructed to perform a series of movements (such as marching on the spot - yes you heard right) to insure an even distribution.
Dihydroxyacetone (DHA) is the active ingredient used in the solutions administered by the booths. The DHA once on coming into contact with the skin reacts with amino acids present in the epidermis layer of the skin. This reaction produces a natural pigment called melanoidin which bonds with the proteins contained in the skin cells. DHA only penetrates the upper part of the epidermis (stratum corneum.) A tan will fade as skin cells are shed and future sessions will be needed.
General opinion is that although pose the option of a faster evenly applied tan, nothing can beat the use of the simple airbrush system in the hands of a professional. Think about it - some areas of our bodies are exposed to "the sun" more than others such as our cheekbones and the top of our shoulders. A professional can add more solution to these areas creating a more personalised look, and unlike a tanning booth which is set up with "the masses" in mind a simple airbrush method can be individual specific. The positive aspect of booths though, is that it does offer some privacy; standing near naked in front of a stranger who is spraying over every inch of your body is not for everyone.
Solutions used in sunless tanning booths do not often contain any effective sunscreen of UV filters that protect our skin from UV exposure. These solutions, although they darken the skin, are by no means helping the production of Vitamin D which is only facilitated by direct UV exposure. As previously stated, booths cause a pigment melanoidin to be produced. Melanoidin and melanin (what causes a real tan to develop from direct UV exposure) do share a link in their absorption spectra. This means that a self tan can provide a SPF rating of about 2. This is not high enough to adequately protect the skin and a sunscreen or sun block should always be used.