Your Body: The Missing Manual

Chapter 1. Skin: Your Outer Layer

Every practical person knows the value of a good outer layer. That’s why you wear a raincoat when you visit London, use plastic wrap to save today’s dinner for tomorrow’s lunch, and don a ski mask when you climb snow-capped mountains (or make an unscheduled withdrawal from someone else’s bank account). But by far, the most impressive covering you’ll ever encounter is your skin—the 8 to 11 pounds of watertight wrapping that covers virtually every square inch of your body.

Skin does far more than the obvious task of keeping your insides on the inside. It’s a washable, stretchable, self-repairing fabric that lasts a lifetime with minimal care. It’s also home to a few other important bits of human machinery, including your hair, nails, and sweat glands. Removed and laid flat, your skin occupies about 20 square feet of space—enough to cover the top of a twin-size bed and make it the surprise winner of the “largest organ in your body” award.

Learning about your skin is a great way to spend a Sunday afternoon (and a surefire way to impress your dermatologist). That’s because the study of skin holds secrets that can help you smell nicer (Body Odor), stave off wrinkles (Wrinkles), and commit the perfect crime (see the box about fingerprints on How Fingerprints Work). In this chapter, you’ll learn everything you need to know to care for your very own body wrapper.

The Protective Wrapper

When people think about the purpose of skin, most settle on the obvious—the ...