Dry Aging Skin - What is it?

What is the skin barrier?

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

Your skin barrier is what you can see and touch on the surface of your body.

Your skin barrier protects you from physical, chemical, and microbial insults, and prevents the loss of water from your body.

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.

Learn More: What is The Skin Barrier?

What is the stratum corneum? "The brick wall"

The stratum corneum is the most outer layer of the skin.

The stratum corneum can be thought of as a brick wall that protects you.

The "bricks" are the skin cells, called corneocytes, and the "mortar" that holds the bricks together is the lipids or fats, that together create the outer barrier.

The stratum corneum is the most outer layer of the epidermis and is the layer directly exposed to the external environment.

What is the stratum corneum made of?

On a weight basis, the stratum corneum contains approximately 70% protein, 15-25% water and 15% lipids (Ananthapadmanabhan et al, 2013).

The structure of the stratum corneum can be described as a ‘brick and mortar’ model, in which the protein-rich corneocytes are the bricks, and the mortar is the lipid‐rich matrix containing ceramides, cholesterol, and fatty acids.

The skin barrier includes:

• The moisture barrier
• The lipid barrier
• The acid mantle

What is the moisture barrier?

The skin moisture barrier is a part of your skin barrier. 

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

The skin 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.

Normal skin hydration

Water is essential for the normal functioning of the skin. 

The water content of skin is remarkably high - the epidermis (the outer skin layer) contains more than 70% water, while its outermost layer, the stratum corneum has been shown to contain ~15 - 25% water (Warner et al, 1988; Caspers et al, 2001; Caspers et al, 2003).

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

1. Natural moisturizing factors (NMFs) and other humectants (such as glycerol and hyaluronic acid) to attract and hold onto moisture
2. Intercellular lipids (fats) that form a barrier to prevent transepidermal water loss (TEWL) (Verdier-Sévrain et al, 2007). 

What is the lipid barrier?

The lipid barrier is a part of the skin barrier. 

There are many beneficial fats and lipids that are naturally found in the lipid barrier and skin barrier and play a critical role in keeping your skin healthy.

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

Epidermal lipids include:

• Ceramides
• Free Fatty Acids
• Cholesterol

Epidermal lipids are released from keratinocytes (skin cells), and are a mixture of ceramides, free fatty acids and cholesterol. These lipids are released from skin cells and fill the spaces between the cells, like mortar or cement (Pappas, 2009).

Sebum is made of:

• Triglycerides
• Wax esters
• Squalene

Sebum is an oily, waxy substance produced by your body’s sebaceous glands and eventually released to the surface of the skin. Sebum is primarily made up of non polar lipids as triglycerides, wax esters and squalene. Sebum coats the skin, seals in moisture, and protects your skin from getting too dry (Pappas, 2009). 

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

Beneficial lipids:

• Strengthen the skin barrier.
• Improve the appearance of skin.
• Make skin feel soft and smooth.
• Reduce the appearance of fine lines and wrinkles.
• Relieve dry skin, flaking and scaling.
• Reduce redness and inflammation.

Learn more: Lipid Barrier - Beneficial Fats in The Skin Barrier

What is the acid mantle?

The acid mantle is a part of the skin barrier.

The term "acid mantle" describes the inherent acidic nature of the outer skin barrier, or stratum corneum.

Maintaining skin pH is important, as skin pH influences skin barrier homeostasis, stratum corneum integrity and cohesion, and antimicrobial defense mechanisms. 

Many factors can affect the pH of the skin, including age, sebum, sweat, detergents, cosmetics, and irritation.

The pH of the skin is generally in the range 4.5 to 6.5.

pH numbers refer to the acid, neutral or alkaline nature of the skin. The number is a range from 1 to 14, where 1 is highly acidic and 14 is highly basic (or alkali).

The pH at the surface of healthy adult human skin is slightly acidic, around pH 5 (Schade et al, 1928; Lambers et al, 2006).

The acidic pH is the result of keratinocyte-produced free fatty acids, and components of natural moisturizing factors (NMFs), including urocanic acid, carbonic acid, and keratins (Schmid-Wendtner et al, 2006). 

The pH of the extractable water-soluble components of the skin can be measured. The skin pH and the buffering capacity of the skin surface are made up of the contributions from all the components of the stratum corneum as well as the secretions from sebaceous and sweat glands (Dikstein et al, 1994).

Learn more: What is The Acid Mantle of The Skin Barrier? How Does it Protect You?

What is aging skin?

Aging skin is fragile and is more susceptible to damage and disease. 

As your body ages, the appearance and characteristics of your skin change.

1. Your skin barrier becomes more permeable.
2. Reduction in skin hydration.
3. Reduction in skin lipids and fats.
4. Increase in skin surface pH.

(Choi et al, 2019)

 Aging is accelerated with exposure to sunlight, smoking and pollution.

Why does skin aging occur?

Skin aging can be caused by internal and external factors.

Intrinsic aging occurs with increasing age and is strongly associated with genetic factors (Jenkins et al, 2002). 

Extrinsic aging is caused by exposure to UV radiation (photoaging), air pollution and smoke (Choi et al, 2019).

Intrinsic aging, or chronologic aging occurs naturally. Factors such as disease state, malnutrition, or menopause and your hormone levels can contribute to your skin aging. 

Learn more: Does Menopause Cause Dry Skin on Your Face? Yes

What is dry aging skin?

As early as 50 years of age, the frequency of aging-associated skin disorders increases, in parallel with epidermal dysfunction, including compromised permeability homeostasis and reductions in levels of stratum corneum hydration, as well as elevations in skin surface pH, the most prominent features associated with chronic aging (Wang et al, 2020).

Studies have shown that skin barrier dysfunction can increase your risk of developing eczema (atopic dermatitis), contact dermatitis, pruritus (itchy skin) and xerosis (dry skin) (Wang et al, 2020).

Dermatoses such as xerosis (dry skin), pruritus, and eczema are also widespread in the elderly, create substantial suffering in those afflicted, and are often resistant to treatment (Farage et al, 2009).