There was a time when it was rare for a doctor to come across a tattoo or other form of body art when they examined a patient. But as tattoos have increased in popularity due to their mainstream acceptance as a form of self-expression, this is no longer the case.
The latest research into the prevalence of tattoos shows that between 11.7 and 31.5 per cent of the population in western countries has tattoos. In Europe, tattoos and permanent make-up are estimated to feature among 10–20 per cent of the general population. In the United States, tattooing is even more popular, with a general prevalence of 31 per cent – rising to about 50 per cent among younger age groups.
Tattoos are generally considered safe, but growing scientific evidence suggests tattoo inks are not biologically inert. The key question is no longer whether tattoos introduce foreign substances into the body, but how toxic those substances might be, and how any potential effects might unfold over time.
Writing recently in The Conversation, Dr Manal Mohammed, senior medical microbiology lecturer at the University of Westminster, says tattoo inks are complex chemical mixtures. “They contain pigments that give colour, liquid carriers that help distribute the ink, preservatives to prevent microbial growth, and small amounts of impurities,” she writes.
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It turns out that many pigments currently in use for tattoos were originally developed for industrial applications such as car paint, plastics and printer toner, rather than for injection into human skin. Some inks even contain trace amounts of heavy metals including nickel, chromium, cobalt and occasionally lead. Heavy metals can be toxic at certain levels and are well-known for triggering allergic reactions and immune sensitivity.
Like any procedure that punctures the skin, tattooing carries a risk of infection. Poor hygiene practice in a tattoo studio can lead to infections such as Staphylococcus aureus and hepatitis B and C. Other well-documented health risks of tattoos are allergic and inflammatory reactions. Red ink is particularly associated with persistent itching, swelling and granulomas. Granulomas are small inflammatory nodules that form when the immune system attempts to isolate material it cannot remove.
A particular concern to scientists such as Mohammed is how tattoos might affect our immune system. Tattooing involves injecting ink deep into the dermis, the layer of skin beneath the surface. The body recognises pigment particles as foreign material. Immune cells attempt to remove them, but the particles are too large to be fully cleared. Instead, they become trapped inside skin cells. However, tattoo ink does not remain confined to the skin. It can migrate through the lymphatic system and accumulate in lymph nodes – small structures that filter immune cells and help co-ordinate immune responses.
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“The long-term health effects of ink accumulation in these tissues remain unclear, but their central role in immune defence raises concerns about prolonged exposure to metals and organic toxins,” Mohammed says.
One recent study suggests that commonly used tattoo pigments can influence immune activity, trigger inflammation and reduce the effectiveness of certain vaccines, including a reduced response to Covid-19 vaccine. It suggests tattoo pigments could interfere with immune signalling, the chemical communication system immune cells use to co-ordinate responses to infection or vaccination.
Could tattooing cause cancer?
There is no convincing evidence to suggest it can. Any potential link to skin cancer, such as malignant melanoma, has been firmly discounted. With a large fraction of tattoo ink particles ending up in the lymph nodes, could there be an increased risk of malignant lymphoma (a rare cancer of the lymphatic system) in people with tattoos? A recent Swedish study suggested a possible link, but not a convincing one.
For most people, tattoos do not cause serious health problems. But as tattoos become larger, more numerous and more colourful, cumulative exposure becomes a concern.
When combined with sun exposure and ageing, this burden may have consequences that science has not yet fully uncovered.
