Skin can help diagnose disease:
"Skin is a very powerful reflector of your overall health and well-being," Day said. "If you have a liver or kidney disease, diabetes, heart issue -- it has a way of showing up in skin."
Indeed, Rehana Ahmed, a dermatologist in Edina, Minn., said she has often diagnosed thyroid disease by examining patients' eyebrows, and once by looking at leg hair. "About a third of the eyebrow can stop growing" because the body is conserving hormones used both for hair growth and thyroid function, she said. The skin can also offer clues to depression and Obsessive-Compulsive Disorder, Day said.