Skin does more than present one's" face" to the world; it plays a vital role in the maintenance
of physical and mental health. As our most ancient interface, skin retains the ability to
respond to both endogenous and exogenous stimuli, sensing and integrating environmental
cues while transmitting intrinsic conditions to the outside world. As such, it has long been a
target for the application of both medical and nonmedical therapies of healthy and diseased
states. Our understanding of how the skin and topical therapies affect health is in its infancy …