A recent study confirmed that tattoos can inhibit the secretion of sweat by our sweat glands under thermal stress.
Although the harmful effects of tattoos in the short term are well known (discomfort, erythema, bleeding, and inflammation) and usually disappear within a few weeks, there are still questions about the long-term effects of tattoos. According to a recent study published in The Journal of Applied Physiology, tattoos interfere with the production of sweat from our sweat glands.
A phenomenon that has already been suspected
Previous studies had already identified the phenomenon in conditions that were not free from limitations and methodological distortions that made it difficult to draw firm conclusions. For example, it was already known that tattoos induced a lower production of sweat and that this sweat was much more concentrated with sodium chloride. Therefore, there was a concern of adverse effects during physical activity or high temperatures, especially regarding thermal homeostasis and sodium absorption. However, in another experiment, during a 20-minute exercise, no difference was observed in the production of sweat between tattooed and untattooed skin.
But this type of approach has great methodological limitations, as the authors of the study explain: “It is difficult to determine the magnitude of the thermal stimulus of this exercise since neither the internal temperature nor the skin temperature was measured. It is possible that the 20-minute exercise is not a sufficient thermal stimulus to distinguish possible differences in the sweat rate between tattooed skin and healthy control skin.”
Consequently, our experimenters have developed a method that is already used in the world of physiological research: passive heating of the whole body. The subjects of the study (5 women and 5 men) put on a suit and laid down on a medical bed. The suit was infused with 34°C of hot water for 10 minutes, then the entire body is passively heated by injecting 48°C of hot water through the suit until the participants’ intestinal temperature rose by 1.0°C. Using this methodology, they were able to evaluate their initial hypothesis that reflex increases in sweating rate and skin vasodilatation would be impeded on the tattooed part of the skin compared to the adjacent non-tattooed part during passive whole-body heating.
Tattoos could damage our eccrine sweat glands
In the experiment, intestinal and skin temperature, blood flow, and the sweat rate were measured during the reference phase at 34°C and in the passive heating phase. The results showed that the sweat rate on the tattooed part of the participants’ skin was lower than on the untattooed part. However, the tattooed skin still sweats and the time it takes for sweat to appear is identical between the tattooed and untattooed skin.
This suggests that the tattoo could indeed cause side effects within the eccrine sweat glands. Some researchers hypothesized that the tattoo could make our glands less sensitive to acetylcholine, a neurotransmitter whose function is to signal our glands to start sweat production when faced with thermal stress. In fact, the hypothesis of a change in the neural circuit is questioned by the above experience, since perspiration is still present and time delays for the occurrence of perspiration are similar. If there had been a change in the neurological signal, different results would have been obtained.
The authors believe that these results have implications for the long-term risks of tattooing, especially for those that are more susceptible to thermal stress, such as professional athletes and military personnel. They concluded that the reduction in perspiration from tattooed skin may affect heat dissipation, especially if the tattoo covers a larger percentage of the body’s surface.