works through a process of DHA, which is a sort of coloring approved by the FDA. It has been around for about 50 years. Farmers used to put it on fruits and vegetables to make them appear riper for market. We have been consuming it for a long time. It takes a couple of hours to make the skin appear tanned. Generally speaking it lasts about 4-6 days in the mountains or 7-9 days in a place with high humidity before it begins to wear off.
If you make a mistake, a self tanner has to wear off (unless you really want to dry the skin). If you act immediately, you can use a towel or sponge, but once on you it's very hard get rid of. I haven't found anything that will strip it off immediately. You should see my hands sometimes