Slinging ink, raising temperatures

DALLAS (SMU) - You've heard that they can sag with age, perpetuate the name of a regrettable ex, or reveal an embarrassing inability to spell. But tattoos may also impair the way we sweat, potentially causing the body to overheat if the tattoos cover a large area of the body.

A team of researchers that includes SMU physiologist Scott L. Davis outlined the connection between tattoos and damage to sweat glands in a study published in the Journal of Applied Physiology. Their study of tattooed skin and adjacent non-tattooed skin on the arms of an evenly-divided group of men and women found that the tattooed sections of skin had reduced sweat rates. 

That's a potential problem because sweating is how the body cools itself and regulates its temperature.

"Any damage to eccrine (sweat) glands within the skin can impair sweating response and potentially increase the risk of overheating if the damage covers a large enough body surface area," Davis said.

Eccrine sweat glands, which are found in most skin across the body, produce sweat to cool the body. The human body must regulate its temperature for survival.

Davis, associate professor in applied physiology and wellness at SMU's Simmons School of Education and Human Development, collaborated for the study with researchers from Alma College, the University of Texas Southwestern Medical Center and the University of Kentucky College of Medicine.

In the study, they determined sweating rates in the upper and lower arms of people with tattoos by comparing at least 5.6 square centimeters of tattooed skin with adjacent non-tattooed skin. Ten people - both men and women - participated in the study. 

These volunteer subjects wore a special tube-lined suit that circulated hot water in excess of 120 degrees Fahrenheit for 30 minutes to increase core temperatures and measure the level of sweating. Tattooed and non-tattooed areas of skin both began to sweat at around the same time. But tattooed areas ultimately produced less sweat than areas without tattoos. 

The findings suggest that even though nerve signals to sweat glands weren't affected in tattooed skin, the sweat glands themselves were likely damaged during tattooing. 

Tattoos are made permanent by injecting ink through the thin layer of outer skin into the middle layer of skin known as the dermis, which contains connective tissue, hair follicles and sweat glands. Applying a tattoo typically requires puncturing the skin with needles 50 to 3,000 times per minute, at a depth of 1-5 millimeters which could result in sweat gland damage.  

"These data indicate that the collateral effects of the tattooing process negatively impact eccrine sweat gland function and could be considered a potential long-term complication or side effect of this cosmetic procedure," researchers wrote. 

###

SMU is the nationally ranked global research university in the dynamic city of Dallas. SMU's alumni, faculty and over 12,000 students in eight degree-granting schools demonstrate an entrepreneurial spirit as they lead change in their professions, communities and the world.