Video Explains How Moisturizers Work to Soothe Dry Skin

The three classes of moisturizers. American Chemical Society

A lot of people develop dry skin in the winter, and turn to moisturizers. But do you know how they actually work?

This video from the American Chemical Society explains it nicely:

The body's blood vessels supply water and moisture to the dermis, the middle layer of skin. From there, the moisture travels to the epidermis, the outer layer. This is what you see covering your body; the dermis is typically only exposed if you get scraped or scratched. Moisture is lost through transepidermal water loss, mostly via evaporation.

Moisturizers are divided into three types: occlusives, emollients and humectants. Some products may contain all of these, or any variation thereof.

Occlusives include products like petroleum jelly, and these chemicals form a protective barrier that prevents moisture from evaporating.

Emollients are chemically similar and often contain fatty acid chains, a good example being castor oil. They are designed to penetrate into the skin, making it feel softer and less itchy, which makes them sufficient for treating many cases of the common skin problem eczema. They also fill gaps left by protein chains damaged by excessive water loss.

Finally, humectants are absorbed by the epidermis and help attract and retain moisture. They can also increase production of waxy chemicals called ceramides that help prevent water loss. One drawback to humectants is that some of them can increase moisture evaporation by enhancing water absorption from the underlying dermis, exposing it to the air and elements. So for that reason they are usually combined with occlusives, according to a 2005 paper on moisturizers.