Tattoo: Ancient art and current problems.

The popularity of tattoos in the today's society brings with it a significant increase of the incidence of associated cutaneous reactions. Among the several complications that may occur after a tattooing procedure, allergic and photo-allergic reactions, infections, and Koebner phenomenon are the most common ones observed. Most of these complications may be avoided by identifying, before tattooing, the presence of risk factors or comorbidities that may increase the risk of their onset.