Tattoos may permanently alter the physiology of skin in ways that affect sweating.
According to a small, new study, the amount and saltiness of sweat change after skin has been dyed, a finding that might have implications for athletes who ink large swaths of their bodies and maybe even for those of us who sport one or two discreet tattoos (such as the small one on my right shoulder, in case you were wondering).
Tattoos are decorative, often metaphoric, sometimes regrettable, but always injurious. To create a tattoo, the artist punctures the skin with dye-filled needles at a rate of up to 3,000 times per minute. The dye is injected into the skin’s dermal layer, which is also where most sweat glands are.
The body recognizes these injections as abnormal. They have slightly damaged the tissue and left behind a foreign substance, the ink. So the immune system gears up, sending a variety of cells to the site of the inking. Some cells carry off tiny amounts of the ink, primarily to the lymph nodes, where it dissipates. Other immune cells merge with the remaining ink, so that both become long-term residents of that portion of the skin. Still other cells initiate an inflammatory response, helping the injured tissue to mend, which it usually does within a few weeks.
As anyone who watches sports knows, tattoos are popular with athletes. By some estimates, at least half of male collegiate and professional basketball players have tattoos that cover much of their chest and arms. The incidence seems to be high among football and soccer players and many other athletes as well.
But no one had studied whether tattoos might in any way affect the physiology of the skin and, in particular, the operation of the sweat glands. That possibility matters, since normal, healthy sweat glands are important for athletes (and everyone else). We cool our bodies in large part through sweating. Sweating also releases sodium and other electrolytes.