If the sun's rays don't do anything, what makes your skin look darker? According to Jules Von Hep, celebrity spray tanner and co-founder of self-tanning brand Isle of Paradise, the main ingredient in spray tanning formulas is DHA. "This reacts with your amino acids and gives the illusion of a tan. DHA is like milk. It can come in many different forms - think full fat, skim, 1%, organic. In my experience , Organic DHA works best.”