The American Journal of Human Biology has just published an article online (ahead of print) by Dr. Christopher Lynn, Johnna Dominguez (MA, 2015), and Dr. Jason DeCaro entitled “Tattooing to ‘Toughen Up’: Tattoo Experience and Secretory Immunoglobulin A.” http://onlinelibrary.wiley.com/doi/10.1002/ajhb.22847/abstract
Objectives: A costly signaling model suggests tattooing inoculates the immune system to heightened vigilance against stressors associated with soft tissue damage. We sought to investigate this “inoculation hypothesis” of tattooing as a costly honest signal of fitness. We hypothesized that the immune system habituates to the tattooing stressor in repeatedly tattooed individuals and that immune response to the stress of the tattooing process would correlate with lifetime tattoo experience. Methods: Participants were 24 women and 5 men (aged 18–47). We measured immune function using secretory immunoglobulin A (SIgA) and cortisol (sCORT) in saliva collected before and after tattoo sessions. We measured tattoo experience as a sum of number of tattoos, lifetime hours tattooed, years since first tattoo, percent of body covered, and number of tattoo sessions. We predicted an inverse relationship between SIgA and sCORT and less SIgA immunosuppression among those with more tattoo experience. We used hierarchical multiple regression to test for a main effect of tattoo experience on post-tattoo SIgA, controlling for pretest SIgA, tattoo session duration, body mass, and the interaction between tattoo experience and test session duration. Results: The regression model was significant (P = 0.006) with a large effect size (r2 = 0.711) and significant and positive main (P = 0.03) and interaction effects (P = 0.014). Conclusions: Our data suggest that the body habituates over time to the tattooing stressor. It is possible that individuals with healthy immune systems heal faster, making them more likely to get multiple tattoos. Am. J. Hum. Biol., 2016. © 2016 Wiley Periodicals, Inc.