A UV tattoo is made using ultraviolet (UV) reactive ink. The design or lettering is tattooed in the skin using this special ink, which is only visible under UV light.
UV tattoos, also called blacklight tattoos, are a relatively new concept. Because the potential health concerns are yet unknown, many tattoo artists do not offer this service, writes Karen L. Hudson for About.com. The UV tattoo is usually invisible under normal light, but then shines in various colors when under blacklight or UV light. Many times, only a portion of a visible tattoo has UV effects, such as a black tattoo skull that has UV-tinted eyes. So, when under a UV light in the dark, the colored eyes shine brightly.