Tattoos have become a popular phenomenon, and it is estimated that up to one in three young adults have been under the needle. New studies suggest that long-term exposure to tattoo ink may increase the risk of cancer.
We know that tattoo ink migrates from the skin and accumulates in the surrounding lymph nodes. We expect that a persistent immunological response is initiated in ink-affected lymph nodes and suspect that this burden on the body can lead to dysfunction of the lymph nodes and thus be carcinogenic. Therefore, it is not only the carcinogenic ingredients in tattoo ink that raise concern, but the presence of a foreign body in the lymph nodes (regardless of ink color).
New studies suggest that there is an increased incidence of certain types of cancer among tattooed individuals
A solid, Swedish study from May 2024 showed a strong indication of an increased incidence of lymphoma (lymphatic cancer) among tattooed individuals, and a study from Utah from October 2024 pointed to an increased risk of a specific type of lymphoma among tattooed individuals. Most recently, a Danish study from January 2025 showed an increased occurrence of skin cancer and lymphoma among tattooed individuals (This study is based on data from the Danish Twin Tattoo Cohort, which is described in more detail below).
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Future research
Based on these studies, we find significant evidence of an association between tattoos and the occurrence of lymphoma, but we are unsure of the extent of its impact. To increase our knowledge in this area, we therefore wish to investigate which types of lymphoma are particularly sensitive to tattoo ink and how lymph nodes biologically react to a foreign substance like tattoo ink, with the aim that existing and new knowledge together can form the basis for preventive measures.
The association between tattoos and cancer types is extremely difficult to investigate, partly because the development time for lymphoma can be long, and because many factors are involved. Additionally, such a study requires access to population-based registers with information on cancer diagnoses, (which are lacking in many parts of the world) - and information about tattoos which comes from surveys (where representative participation is important).
The Danish Twin Tattoo Cohort
In 2021 we took the initiative to establish the Danish Twin Tattoo Cohort with the aim of investigating:
- i) the increasing popularity of tattoos and the factors influencing tattoo behavior, and
- ii) whether tattoo ink can be related to the occurrence of certain cancers such as skin cancer and lymphoma.
We conducted a questionnaire survey among 11,100 Danish twins. In this survey we asked questions about tattoos, lifestyle, and education. In relation to the above-mentioned study of cancer, the collected data were linked to information on cancer diagnoses from The Danish Cancer Registry.
Tattoo behavior among Danish twins
The first study, which focuses on tattoo behavior, describes, among other things, that 4 out of 10 women and 3 out of 10 men are expected to have tattoos by the age of 25. The study also shows that cultural influence, such as one's social circle, has a significant impact on the decision to get the first tattoo, while one's genes have a very limited impact.
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The association between tattoos and cancer
The second study based on data from the survey investigates whether there is an association between tattoos and the occurrence of certain cancer types using so-called hazard rates. Here, we find an increased occurrence of skin cancer among tattooed individuals. The association is most pronounced among people with large tattoos (larger than the palm of a hand). Additionally, we find an increased occurrence of lymphoma among people with large tattoos. In this study, no association is observed for any of the cancer types when looking exclusively at tattoos with red ink. However, this should be further investigated in larger studies.
In the statistical analyses in this study, we use an approach that can account for many other unknown factors that may also lead to the same cancer types. In this approach we study twin pairs where we know that at least one twin has been diagnosed with the cancer in question. The big question is whether both twins in a pair have tattoos or not, and if they have, what colors and sizes of the tattoos are, and for how long they have had the tattoos. In the statistical analyses, time-varying effects are taken into account, for example, by using the age at which people got their tattoos.
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Financing
The survey was carried out in collaboration with:
Danish Twin Research Center
Contact persons
- Assistant professor in biostatistics,
- Professor in biostatistics,
- Clinical professor and consultant in hematology,