Nickel and tattoos: Where are we?

Tattoos are not mentioned as a source of exposure to nickel. Traces of nickel are, however, almost inevitably found in tattoo inks as impurities and sometimes in tattooed skin. Whether nickel in tattoos has any health consequence is debated. We performed a narrative review of what is currently known about this topic. Today, nickel is frequently detected in inks, but at highly variable levels. It appears to be at higher concentrations in green, blue, and sometimes brown and violet inks. Only nickel allergy in tattooed individuals and nickel-associated tattoo ink allergy are addressed in the literature. Reports of tattoo ink allergy related to nickel are rare and heterogenous. Authors often neglect possible implications of other metals or dyes. A positive patch test is not enough to confirm the role of nickel in a reaction observed after tattooing. We found no report of any systemic complication attributed to nickel from tattoos. The Council of Europe ResAP(2008)1 bans the presence of nickel at high levels in tattoo inks, which is a safety net for individuals with nickel allergy. Large epidemiologic case-control studies with systematic biopsies on normal and inflamed tattoos and patch testing would help to understand the role of nickel in tattoo ink allergies.