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Why do you have dry skin?


Image: Nathan Dumlao, Unsplash

Many reasons for dry skin. Diet. Lifestyle. Environment. Illness. Your skin is dry.

Let us talk about that last point. You have dry skin because your skin is dry. Your skin type is dry (as opposed to oily or normal or something else).

How do you know if your skin type is dry skin? If you have always had dry skin then most likely you have that type of skin, although this is not necessarily true.

What makes skin a dry skin type? To understand that, let us look at basic skin science.

Layers of the skin

The skin acts as a defence mechanism that prevents the loss of water from the body. It does a lot of other important things. But those are not going to be addressed here.

It is made of three layers. The outer visible layer is the epidermis. The dermis, the middle layer, provides a supporting role. The hypodermis is made of fat.

The epidermis is further sub-divided into five layers. The outer layer is the stratum corneum (SC). This is what you can touch and see.

The primary building blocks of the epidermis, keratinocyte cells, are created at the base of the epidermis. They multiple and move through the five layers. By the time they reach the SC layer, they are dead and fall off to make way for more keratinocytes. The shedding or peeling of keratinocytes is called desquamation and is unnoticeable in normal skin.

The protective outer layer of skin

The SC is the very first layer of the strong protective barrier that prevents water escaping from the skin.

The SC’s strength comes from corneocytes, dead keratinocyte cells. Each corneocyte, containing keratin proteins, is wrapped in a protective coating called the cornfield cell envelope (CE). The keratin and the CE help give the corneocyte its strength.

Corneocyte also contain natural moisturizing factor (NMF). NMF is made of amino acids and its by-products such as pyrrolidone carboxylic acid (PCA), urocanic acid (UCA), lactic acid, urea, citrate, sugars. It act as a humectant. Humectants love water. They attract and mix with water from the atmosphere. They also dissolve in water. They keep skin moist and hydrated.

The corneocytes are held together by layers of fat. These layers of fat are made of fatty acids, ceramics and cholesterol. The fat acts as the protective barrier and prevents NMF and water from escaping through the skin.

What does all of the above have to do with dry skin?

Healthy, moist, hydrated skin has more than 10% water in the SC layer. Dry skin has less than that because it has been lost somehow.

Water loss occurs because the strong protective skin barrier is damaged, there is not enough fat or NMF. Skin that lacks moisture is stiff, full of lines, wrinkled or cracked, and may have white patches (improper desquamation). It is dry.

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