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Skin tattooing impairs sweating during passive whole-body heating.

Tattooing of the skin involves repeated needle insertions to deposit ink into the dermal layer of the skin, potentially damaging eccrine sweat glands and the cutaneous vasculature. This study tested the hypothesis that reflex increases in sweat rate (SR) and cutaneous vasodilation are blunted in tattooed skin (TAT) compared to adjacent healthy skin (CON) during a passive whole-body heat stress (WBH). Ten individuals (5M, 5F) with a sufficient area of tattooed skin participated in the study. Intestinal temperature (Tint), skin temperature (Tskin), skin blood flow (laser-Doppler flux; LDF), and SR were continuously measured during normothermic baseline (34 °C water perfusing a tube-lined suit) and WBH (increased Tint 1.0 °C via 48 °C water perfusing suit). SR throughout WBH was lower for TAT compared to CON (p=0.033). Accumulated sweating responses during WBH (area under curve) were attenuated in TAT relative to CON (23.1±12.9, 26.9±14.5 mg×cm-2, p=0.043). Sweating threshold, expressed as the onset of sweating in time or Tint from the initiation of WBH were not different between TAT and CON. Tattooing impeded the ability to obtain LDF measurements. These data suggest that tattooing functionally damages secretion mechanisms, affecting the reflex capacity of the gland to produce sweat, but does not appear to affect neural signaling to initiate sweating. Decreased sweating could impact heat dissipation especially when tattooing covers a higher percentage of body surface area and could be considered a potential long-term clinical side effect of tattooing.