More myths. In modern conditions, tattoos cause only social harm - it is more difficult to find a job and go to the pool in Japan with them. All potential health risks are excluded if the master is adequate, that is, uses disposable consumables where there is at least hypothetical contact with damaged skin, and explains how to take care of the tattoo.
If the tattoo is done in the right conditions, then it will not cause any harm.
If something, as they say, "goes wrong", then not the most pleasant consequences are possible:
Skin irritation resulting in an allergic reaction. Among other things, there may be a reaction to a component in the composition of the paint (be careful and ask a specialist which pigment is used by the company) - it is mainly metal, most often it is found in red shades.
Inflammation. This outcome is possible in two cases:
a crooked master and bad equipment (this can include improper operation of tattoo equipment, sterility during the session, and even sloppy work of a "professional")
improper tattoo care (there are many care products, but not all of them are suitable in the case of tattoo healing, so be careful and better follow the instructions of the master)
Well, you should not forget about diseases for which it is contraindicated to beat a tattoo (blood diseases, high blood pressure, heart disease, skin diseases, and so on)