Tattoos remain one of the most popular ways for people to express themselves — about one in three of us have them — but they might be doing more to your body than showing off your love of flowers, skulls, birds or your ex’s name.
A recent study conducted by Maurie Luetkemeier, a professor of integrative physiology and health science at Alma College in Alma, Mich., and students Joe Hanisko and Kyle Aho found one of the more unexpected tattoo side effects: they can affect your body’s ability to sweat — possibly permanently.
For the study, Dr. Luetkemeier and his team enlisted the help of 10 healthy men with tattoos that covered at least 5.2 centimeters of their skin; some of the men had older tattoos (three or four years old), while some had newer ink. The researchers then applied pilocarpine nitrate, a chemical that promotes sweating, to the tattoo and a matching swath of non-tattooed skin (for example, if the participant had a tattoo on his left bicep, they put the chemical both there and on the non-tattooed right bicep). The researchers then applied a patch over the areas for 20 minutes to absorb the sweat.
The results? The tattooed skin produced much less sweat than the non-tatted skin — some by more than 50 percent. The sweat that did come from tattooed skin was also much higher in sodium.
These results, according to Dr. Luetkemeier, show that tattoos produce a physiological change in the body, either because the ink blocks the sweat glands, or that inflammation sticks around cells in a way that changes how sweat glands react to sweat. He’s planning a larger study to get more expansive data.
And it might cause some people to rethink their large sleeve tattoos or armpit tattoos, which are lauded as the “cute” Instagram trend of summer 2017. The tattoos are interesting — and look pretty painful — but they could cause more problems in the long run, and not only with sweating.
According to Pauline J. Jose, MD, a clinical instructor in UCLA's Department of Family Medicine, armpit tattoos can potentially cause a false positive on cancer tests.
“Tattoo pigments travel through the lymphatic system," Dr. Jose told Health.com. "Since lymph nodes are abundant in the armpit area, [an armpit tattoo] can pigment those lymph nodes, and mimic — or confuse — a cancer diagnosis."
The potential risks might be worth it to die-hard fans, but this is one trend we’ll sit out.