Black light tattoo ink may not be absorbed by the skin the same way conventional inks can. They may not blend the same predictable way as other inks. For this reason, people should only get a U.V. tattoo by an experienced tattoo artist with experience in black light tattoos.
There are many different colors of black light or UV reactive ink. For the titanium white color, in the absence of UV light, the tattoo can be completely transparent on light skin tones. Other colors are visible in any light but glow in black light!
UV ink contains phosphorous, possible carcinogens, and allergens, so there is a risk your body may reject the tattoo. Some people even claim that their once nearly clear UV tattoo has turned brown in a period of a few months.
It's a special tattoo ink that only glows under ultraviolet light. The special ink for black light tattoos contains chemicals that absorb the high energy UV rays for a few nanoseconds. Then the chemicals release the energy and the tattoo glows!
Overall, there has been a statistically higher number of reactions and complications with the UV tattoos than with regular tattoos. In regards to mixing the inks from an existing tattoo with a U.V. tatoo (regular ink with UV ink intermingled and around an existing tattoo), there is a possibility of an adverse reaction.