Many advancements have been made on the sunless-tanning front since 1960, when Coppertone® came out with the first sunless-tanning product — QT® or Quick Tanning Lotion. We no longer have to settle for an orange hue when we make the healthy choice not to subject our skin to the harmful UV rays from tanning beds and the sun! Whether it's a deep and dark tan or a beautiful and radiant glow, we can have it thanks to DHA (dihydroxyacetone)!

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 (up to 10 for some people) from the initial application.

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 about every three days to maintain your "tan." GLOW offers a tan extender, which (for best results) should be used in place of a daily moisturizer in the evenings before bed 2-3 times per week in between you GLOW Airbrush Tanning Sessions!

Thank you http://www.arubatan.com/consumers/c_howdhaworks.html for the information!