Below the surface

The inner life of skin

Photo of a person's back

By definition, skin is superficial. It forms our surface. But skin is anything but one-dimensional.

Beyond its obvious roles of keeping our insides in and the outside out, skin has many less conspicuous duties: Its sweat glands help regulate temperature, its nerves provide the sense of touch, its deeper cells produce vitamin D, and its appearance advertises your age and health.

For those who can read skin’s language, a close examination reveals clues about the whole body’s health. A rash, for example, can indicate allergies; dark, velvety patches can point to diabetes; reddish, star-shaped patterns often mean liver disease; and deep folds in thickened palms suggest lung cancer.

When symptoms appear on the skin, they’re easy to spot — and so are the successes (or failures) of attempts to heal them. This visibility is a boon to dermatologists, speeding their research into diseases and treatments. Among the most recent results are drugs that can cure skin cancers, experimental treatments for an agonizing blistering disease and insights into the genes that keep skin looking young.

And it’s heartening to realize that many of their discoveries have implications not only for skin but also for our less accessible organs.

To get deeper into skin, read on.