Tattoos may do more than decorate the skin — they could also alter how the body responds to disease, according to new research.
Scientists are examining how tattoos may affect the immune system and warn that what might seem a purely cosmetic procedure could influence the way the body fights disease.
A new study by the Institute for Research in Biomedicine at the Università della Svizzera italiana (USI) in Switzerland investigated the toxicity of tattoo inks, focusing on the three most commonly used colours: black, red, and green.
“This work represents the most extensive study to date regarding the effect of tattoo ink on the immune response and raises serious health concerns associated with the tattooing practice,” researchers said.
The study, published in PNAS, found that tattoo ink not only remains in the skin but also travels through the body, accumulating in the immune system, where it can stay for years.
Within these tissues, the ink triggers cell death, as macrophages — key immune cells — cannot digest the captured pigment, causing inflammation that may weaken the body’s defences.
This reaction appeared stronger in tattoos made with red and black ink.
In tests with mice, scientists observed that pigments rapidly travelled to the animals’ lymph nodes, where they accumulated for two months.
Following tattooing, the mice’s immune response to COVID-19 vaccines weakened, although the same inks appeared to enhance the response to a UV-inactivated flu vaccine.
However, the Swiss researchers stated that these findings must be validated through human studies and across different vaccine types.
The International Agency for Research on Cancer (IARC) is also studying the potential long-term health effects of tattooing, particularly its links to immune response, lymphomas, and other cancers.
Often, the pigment particles are nanoparticle-sized and they can move beyond the dermis.Exposure to tattoo ink may be systemic rather than local, according to IARC’s research.
Tattoo prevalence is highest in Europe and the United States, reaching up to 40 per cent among adults under 40. “As this trend grows, the relevance of tattoo safety for public health is increasing proportionally,” the IARC said.
How do tattoos alter theskin?
Tattooing involves injecting ink into the dermis — the deeper layer of skin — using needles that create tiny punctures. This process triggers an immune response, as the body recognises the ink particles as foreign.
The process induces localised inflammation as the immune system attempts to heal the skin injury caused by the needles.
Tattoo inks, composed of colour pigments diluted in a carrier liquid, may contain up to 100 chemicals. While black tattoos are typically done with carbon pigment, colored tattoos typically contain industrial organic pigments originally designed for plastics, varnishes, or paints.
In Europe, the ink has been regulated since 2022 by the Registration, Evaluation, Authorisation, and Restriction of Chemicals (REACH) regulation, which intends to harmonise the legislation across member states.
