Your skin barrier includes the outermost layers of skin, called the stratum corneum.

When your skin barrier is healthy, it feels and appears smooth, soft, and plump.

In contrast, a damaged skin barrier looks dry, rough, dull, and dehydrated, and may become irritated and inflamed.

Your skin barrier includes:

- The acid mantle

- The lipid barrier

- The moisture barrier

- The protein barrier

Desquamation is the natural process of shedding your skin cells.

There are 15 to 30 layers of bricks (corneocytes) in the outer wall (stratum corneum).

Corneocytes are matured from skin cells called keratinocytes, which populate the lower levels of the skin barrier.

New skin cells are formed at the base layer of the skin, and they differentiate and migrate towards the skin surface, in a process that takes approximately 30 days.

Nearly a billion cells are lost each day from the surface of adult skin. 

The protein layer is critical for the skin’s structural integrity, made of proteins like collagen, elastin, and keratin.

It helps maintain firmness, smoothness, and elasticity, and supports the skin’s overall strength.

Corneocytes are mostly made up of the protein keratin, which is also found in hair and nails.

Corneocytes in the stratum corneum are filled with keratin filaments as well as amino acids (AAs) and other small molecules, collectively referred to as natural moisturizing factors (NMFs), derived from the breakdown of filaggrin, a protein that surrounds the keratin filaments.

The surface of your skin is covered by a layer of beneficial fats, including epidermal lipids and sebum.

These natural fats and lipids help to lubricate and coat your skin cells and nourish your skin.

To protect your lipid barrier:

- Use emollients for dry skin

- Use carrier oils for dry skin

- Use linoleic acid for dry skin

Water is essential for the normal functioning of the skin. 

The skin's moisture barrier ensures your skin is hydrated by trapping and holding water into your skin.

The skin's moisture barrier is composed of water, natural moisturizing factors (NMFs) and other humectants, such as glycerol and hyaluronic acid to attract and hold onto moisture.

The water content of skin is remarkably high - the epidermis contains more than 70% water, while its outermost layer, the stratum corneum has been shown to contain ~ 25% water.

Adequate hydration of the stratum corneum serves three major functions:

1- it maintains plasticity of the skin, protecting it from damage

2- it contributes to optimum stratum corneum barrier function

3- it allows hydrolytic enzymes to function in the process of desquamation

When the water content of the stratum corneum falls below 10%, scaling on the skin surface becomes visible.

Your skin's acid mantle describes the inherent acidic nature of the outer skin barrier, also known as the stratum corneum.

The pH of the skin barrier is slightly acidic, in the range 4.5 to 6.5.

Your skin pH influences:

- Skin barrier function

- Desquamation or shedding of skin cells

- Protection against pathogens "bad bacteria"

A proper skin pH is important to maintain healthy skin.

To prevent dry skin, you must protect your skin barrier, including your skin's moisture barrier, lipid barrier and acid mantle.

To protect you skin's moisture barrier, drink water, use a humidifier, use a moisturizer with humectants. protect your skin from wind, cold weather and sun exposure, and always wear sunscreen or sunblock, especially when you go outside.

To protect your lipid barrier, use emollients for dry skin such as carrier oils rich in linoleic acid.

To protect your skin's acid mantle avoid high pH soaps, use a gentle cleanser and try an oil cleanser.