The U.S. FDA has tested henna nd it has been found to have no harmful affects on people.
The result of the study was that it was so benign that they just didn't make any ruling on it at all. It has been found to be so safe for hair that no further testing is necessary.
It is legal to apply to the hair-hello-you have skin where your hair grows.
So technically, it is not approved for skin just hair.
Since it was found to be non toxic it was just left in sort of limbo.
It is legal to import for hair use.
So it is just like thousands of other silly and unenforceable laws,
in a california town it is illegal to ride a bike in a swimming pool, in another it is against the law to drive more than 2000 sheep down Hollywood Blvd., in Arizona donkeys may not sleep in bathtubs, Denver says it is illegal to lend your vacuum cleaner to another, and in Tennessee it is illegal to shoot any game from a moving vehicle other than whales, and women may not drive unless there is a man wlking/or running in front of her waving a red flag.
So the small issue of whether applying henna to the skin or the hair is legal definately another silly law.
Most places where I apply henna do have some hair on them too........
Flavia