The epidermis is the top layer of skin that is exposed to the external world. It’s what you see and touch of another person.

It’s also like a shield, protecting against wind, rain, cold, and heat, as well as other elements. The epidermis also protects the body from bacteria, viruses, parasites, and other infectious organisms.

Specialized white blood cells in the epidermis (called Langerhans cells) are the primary defense agents in the skin.

Melanin — the pigment that gives skin its color — is also found in the epidermis. The amount of melanin a person has in his or her skin (as well as hair and eyes) determines its shade. Higher concentrations of melanin produce darker skin and skin that tans more easily and quickly.

New skin is continually being made in the epidermis. Every day, old and injured skin cells are replaced with new ones. In fact, it’s estimated that approximately 40,000 old skin cells are shed daily and have to be replaced.

If everything is working well, you get a whole new skin layer every month. Needless to say, the epidermis is a very active part of this system.