SKINIPEDIA - Skin Encyclopedia: Epidermis of the Skin

Skin Physiology 101: A Tour Through the Layers of the Skin

This article brought to you by Michelle Macomber, a San Diego based aesthetician par excellence and the owner of the best facials in San Diego, Surface Esthetics.


THE EPIDERMIS - Your epidermis (skin) is what we work on in the treatment room. It is designed to constantly keratinize, or shed. As you age this process of keratinization slows down, so you need to increase exfoliation in order to get healthy, new epidermal cells.

All of the different “stratums” are how we characterize the cell appearance as it is keratinizing (dying). At each stage, cells lose more and more water through a process called Transepidermal Water Loss (TEWL). You must replace that moisture loss externally, since internal structures cannot feed the epidermal tissue to make up for lost moisture. It is essential to use a moisturizer in order to replace missing moisture, and bind existing water molecles.

Figure 1- The Layers of the Epidermis

The best way to exfoliate is to use Alphahydroxy Acids (AHA’s) or enzymes. These two substances will digest dead skin cells with minimal irritation. Glycolic acid tends to be the most irritating, since the molecules are smallest. These tiny glycolic molecules tend to penetrate the stratum germinativum where the new skin cells grow. When these cells are irritated, it causes a cellular reaction that can lead to hyperpigmentation, or scarring for darker skin types. Use a lactic acid exfoliant in order to minimize irritation. The skin recognizes Lactic acid, as parts of the skin are made up of lactic acid compounds. Therefore, it will respond to the request to shed without irritation.