People have decorated their bodies with tattoos for millennia for ceremonial and religious reasons, and many people today use them as a form of self-expression. Tattoo inks are usually made of a mixture of solid particles, molecular dyes, binders and water. The color of the tattoo comes from light being reflected or absorbed by the particles and dyes. While tattoo artists must be licensed to operate for safety reasons, the inks used for tattoos are unregulated in the U.S.

Researchers from Binghamton University, in New York, analyzed almost 100 inks and found that even when these products included an ingredient label, they were not accurate. The team also detected particles that could be harmful to cells.

“Every time we looked at one of the inks, we found something that gave me pause,” says John Swierk, Ph.D., the project’s principal investigator. “For example, 23 of 56 different inks analyzed to date suggest an azo-containing dye is present.” Although many azo pigments do not cause health concerns when they are chemically intact, bacteria or ultraviolet light can degrade them into another nitrogen-based compound that is a potential carcinogen. In addition, the team analyzed 16 inks using electron microscopy, and about half contained particles small enough to get through the cell membrane and potentially cause harm.

Once this data has been peer reviewed, the findings will be posted at WhatsInMyInk.com to help consumers and artists make informed choices.