There are toxic materials in the composition of some paints. For example: denature alcohol and aldehyde. These materials could be really dangerous for the health of the person who covers his body with that kind of paint. Especially when that person has allergies, he risks making them worse. Once the paint has gone underneath the skin, it will be really hard for him to handle the allergy.
Some materials do not show any symptoms of an allergy right away. There are cases of skin reactions from red ink which contains red ochre, red quicksilver or red cadmium. There are some paints that can cause an allergic reaction after ten years from the making of the tattoo.
The tattooists should use only paints of high quality and a long sell-by date. These paints might be expensive, but they for sure are harmless. A danger might appear only when a tattooist buys cheap paints of low quality at his own risk or when he uses stationery paints instead of specialized.
A good tattooist would never use such paint that can harm his clients. The paints of high quality are a sign of a well done job and a perfectly done tattoo.
Nowadays high quality paints could be found everywhere very easily. So the toxic unhealthy paints are a result of the cooperation of conscienceless manufacturers and tattooists who play with the lives and the health of their clients.