The FDA (Food and Drug Administration) has approved some of the inks used in blacklight tattoos, but has not approved their use as tattoo inks for humans. These inks were originally approved as spectral marking pigment for fish and game. The inks are used to track the movements and migrations of fish and game used for human consumption. Given that testing, the inks may also be safe in human skin but there is no guarantee.

You should be aware of the higher risk of an allergic reaction, as well as the increased amount of time for the application. It is also more difficult for the skin to retain this type of ink. So despite their relative safety, there is no guarantee that once you get a blacklight tattoo, you will not be allergic to the ink, or that your skin will be able to retain it. 

The inks with this kind of FDA approval are sold by Crazy Chameleon Body Arts Supply, and come in 18 colors. 12-18 months until it completely heals and disappears to the human eye.

Any inks that contain phosphorous are not safe! Be sure to find out what is in the ink used by your artist to create a UV reactive or blacklight tattoo! Although they are more than cool when they work, you don't want to risk the health of your skin by using an ink that contains dangerous and poisonous chemicals.