Tattoos Could Be Risk Factor For Melanoma

The state of research on tattoos and cancer

In view of the lack of knowledge concerning the long-term health effects of tattoos, and its position as an under-researched field, researchers at Lund University are examining potential links between tattoos and cancer. The first study, published in spring 2024, showed a possible link between tattoos and lymphoma. A second study was published earlier this year, in which the researchers did not find an association between tattoos and squamous cell carcinoma of the skin.

An increasing number of people are tattooed

Around 20 per cent of all Swedes have been tattooed and for women under 40 the figure is over 40 per cent. Most get their first tattoo between the ages of 18 and 35 but some are even younger, which means almost a lifetime of exposure to tattoo ink. At the same time, the incidence of melanoma has risen considerably over the past 30 years, due to causes such as increased UV radiation, but exposure to chemicals is also a suspected factor. Each year, around 5,000 Swedes are diagnosed with melanoma.

"We don't know about the long-term health effects of tattoos. We therefore need to clarify if there is a link between tattoo ink and skin cancer," says Christel Nielsen, associate professor and researcher in epidemiology at Lund University.

Study design

Using the National Cancer Register, the researchers identified 2,880 individuals who have been diagnosed with melanoma between the ages of 20 and 60. These individuals were then each matched with three individuals from the Total Population Register of the same sex and age but without a melanoma diagnosis. The researchers subsequently collected information via questionnaires about whether the participants were tattooed and controlled for other factors such as sun exposure, sun bed use and skin type. Using this study design, they could estimate the risk of melanoma among tattooed individuals in comparison with non-tattooed individuals and also ensure that the results were not due to other factors such as sun exposure and sun bed use.

Results: Increased relative risk observed at group level

"When we took these factors into account, we saw an increased relative risk among tattooed individuals. Of the participants who had melanoma, 22 per cent were tattooed, compared with 20 per cent in the control group," continues Emelie Rietz Liljedahl, associate researcher in toxicology at Lund University.

This applies at group level but not at individual level. The results suggest that tattoos could be a risk factor for melanoma, but further studies are needed before it is possible to talk about a causal link, emphasises Christel Nielsen.

The impact of tattoo ink

When tattoo ink is injected into the skin, the body perceives it as a foreign substance, which means the immune system is activated. The ink pigments are encapsulated by the immune cells, which hold them in place and transport them via lymphatic fluid to the lymph nodes.

"Azo pigments are the most common organic colourants in tattoo ink. This could be a potential risk because we already know that these can break down into harmful chemicals that may cause cancer. This particularly applies for exposure to UV radiation from the sun, sun beds or laser treatments," says Emelie Rietz Liljedahl.

Regulation of tattoo ink

The tattoo ink market was relatively unregulated until 2022, when an addition to the EU's chemical legislation (REACH) came into effect and introduced concentration limits for chemicals in tattoo ink. Despite this, market surveillance has shown that inks may still contain toxic chemicals exceeding the maximum limits, comments Emelie Rietz Liljedahl.

"In parallel with the authorities' continuing work on regulating the market, we need to understand the potential mechanisms through which tattoos may increase the risk of disease. As epidemiologists, our role is to find patterns in the population. Follow-up studies are now needed to examine why these patterns arise," says Christel Nielsen.

The constantly rising tattoo trend means that the results of the study are more relevant now than ever from a public health perspective. Along with the researchers' previous findings about a possible link between tattoos and lymphoma - but the absence of an association with squamous-cell carcinoma of the skin - the new study takes us one step further in understanding how tattoos may affect our health.

Exploring links to autoimmune conditions

"Our results indicate there may be something that happens in the immune system and therefore we are now going on to continue exploring possible links between tattoo exposure and autoimmune conditions, such as psoriasis and thyroid conditions, in which the immune system is also involved," concludes Christel Nielsen.