Therapeutic Tattoos and Ancient Mummies: The Case of the Iceman

Tattooing as a phenotypic gambit

OBJECTIVES

Tattooing is not an evolved behavior, but it may be a phenotypic gambit to highlight immunological health. Phenotypic gambits are traits or behaviors that appear costly but occur at high rates as a honing process of natural selection not constrained by genetics. Tattooing is an ancient practice that is increasing in popularity worldwide, but it involves wounding the body, which seems counterintuitive because it challenges the immune system and makes one more susceptible to infection. But tattooing may represent a costly honest signal of fitness by "upping the ante" in an era of hygiene or a means to stimulate the immune system in a way that improves and highlights underlying fitness.

MATERIALS AND METHODS

We investigated this hypothesis by assessing bacteria killing activity (BKA) in saliva samples collected during two studies of tattooing (N = 40). We compared previous tattoo experience (extent of body tattooed and hours spent being tattooed) to BKA before and after getting a new tattoo.

RESULTS

Tattoo experience positively predicts post-tattoo BKA (β = 0.48, p = 0.01), suggesting that people with more tattoo experience have a relatively more immediate and active immune response than those with less tattoo experience.

DISCUSSION

Tattoo experience may elevate innate immunological vigilance, which could aid in protecting against future dermal insults.

Topical drug delivery: History, percutaneous absorption, and product development

Topical products, widely used to manage skin conditions, have evolved from simple potions to sophisticated delivery systems. Their development has been facilitated by advances in percutaneous absorption and product design based on an increasingly mechanistic understanding of drug-product-skin interactions, associated experiments, and a quality-by-design framework. Topical drug delivery involves drug transport from a product on the skin to a local target site and then clearance by diffusion, metabolism, and the dermal circulation to the rest of the body and deeper tissues. Insights have been provided by Quantitative Structure Permeability Relationships (QSPR), molecular dynamics simulations, and dermal Physiologically Based PharmacoKinetics (PBPK). Currently, generic product equivalents of reference-listed products dominate the topical delivery market. There is an increasing regulatory interest in understanding topical product delivery behavior under 'in use' conditions and predicting in vivo response for population variations in skin barrier function and response using in silico and in vitro findings.