Aging skin is fragile and is more susceptible to damage.
As you age, several changes in your skin occurs.
Your skin barrier becomes weaker, there is a reduction in skin moisture and lipids, and an increase in skin surface pH levels.
This article will discuss:
- What is aging skin?
- Why does skin aging occur?
- What is photoaging?
- What is the skin barrier?
- What is the moisture barrier?
- What is the lipid barrier?
- What is the acid mantle?
- How does aging affect the skin barrier?
- How does aging affect the moisture barrier?
- How does aging affect the lipid barrier?
- How does aging affect the acid mantle?
- What happens to your skin as your age?
- Summary
- Reviews
What is aging skin?
Aging is the natural process of becoming older as time passes.
Aging skin is fragile and is more susceptible to damage and disease.
Aging is accelerated with exposure to sunlight, smoking and pollution.
As your body ages, the appearance and characteristics of your skin change.
- Your skin barrier becomes more permeable.
- Reduction in skin hydration.
- Reduction in skin lipids and fats.
- Increase in skin surface pH.
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).
Learn more: What is Dry Skin? Medical Definitions and References
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
Intrinsic aging includes:
- Genetic factors
- Health state
- Disease states
- Diet and nutrition
- Exercise levels
- Menopause
Extrinsic aging includes:
- Sun and UV radiation
- Air pollution
- Smoke
What is photoaging?
Photoaging is damage to skin caused by repeated exposure to ultraviolet (UV) irradiation from sunlight (Jenkins et al, 2002).
Photoaging is characterized by morphological changes that include deep wrinkles and loss of elasticity, as well as histological changes such as connective-tissue alterations. These alterations are considered the result of collagen destruction by UV-induced matrix metalloproteinases (MMPs) secreted from epidermal keratinocytes and dermal fibroblasts (Fisher et al, 2002).
Photoaging causes numerous histologic, physiologic, and clinical changes to skin; it also increases the risk for skin cancer.
Photodamage can be prevented through the use of sunscreens, protective clothing, and avoidance of the sun during peak intensity time (Bergfeld et al, 1999).
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).
- it maintains plasticity of the skin, protecting it from damage
- it contributes to optimum stratum corneum barrier function
- it allows hydrolytic enzymes to function in the process of desquamation
- Natural moisturizing factors (NMFs) and other humectants (such as glycerol and hyaluronic acid) to attract and hold onto moisture
- Intercellular lipids (fats) that form a barrier to prevent transepidermal water loss (TEWL) (Verdier-Sévrain et al, 2007).
Water and skin cell turnover
Desquamation is the natural process of shedding skin cells.
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 4 weeks. Nearly a billion cells are lost each day from the surface of adult skin (Milstone et al, 2004).
One of the critical functions of water in the skin is to participate in hydrolytic enzymatic processes required for normal desquamation.
In other words - water is necessary for the enzymes to function properly.
If the skin water content falls below a critical level, the enzymatic function required for normal desquamation is impaired, leading to skin cells sticking and building up on the skin surface (Verdier-Sévrain et al, 2007).
These changes lead to the visible appearance of dryness, roughness, scaling, and flaking (Verdier-Sévrain et al, 2007).
Learn more: What is Dehydrated Skin?
Natural moisturizing factors (NMFs)
The role of the natural moisturizing factors is to maintain adequate skin hydration.
The outer skin layer is called the stratum corneum and it is made up of cells called corneocytes, which form the physical barrier of the skin.
Corneocytes are filled with keratin filaments as well as amino acids and other small molecules, collectively referred to as natural moisturizing factors (NMF), derived from the breakdown of filaggrin, a protein that surrounds the keratin filaments (Verdier-Sévrain et al, 2007).
Natural moisturizing factors are a mix of humectants or hydroscopic molecules that help attract and hold onto water and maintain hydration in the skin.
Natural moisturizing factors include amino acids and their derivatives (pyrrolidone carboxylic acid and urocanic acid) made from the breakdown of epidermal filaggrin. Other components found within but also external to the corneocytes include lactates, urea, and electrolytes (Table 1).
Natural moisturizing factors are present in high concentrations within corneocytes and represent up to 20% to 30% of the dry weight of the outer skin layer (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.
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?
How does aging affect the skin barrier?
As we age, several changes in our skin occur:
- Skin barrier becomes more permeable.
- Reduction in skin hydration.
- Reduction in skin lipids.
- Increase in skin surface pH.
(Choi et al, 2008)
The skin barrier structure changes with aging.
In aging skin, the stratum corneum layers is significantly increased compared with that in younger skin. The epidermis shows remarkable structural changes with aging, which include epidermal thinning (Fisher et al, 2002).
Furthermore, tight junction components that play are role in barrier permeability such as claudin-1 and occludin are also decreased in aging skin (Jin et al, 2016).
An aged epidermis shows various changes that imply skin barrier impairment, such as increased transdermal drug delivery, increased sensitivity to irritants, aggravation of xerosis (dry skin), and development of pruritus (itchy skin) (Fisher et al, 2022; Chung et al, 2003).
How does aging affect the moisture barrier?
The skin's ability to retain moisture diminishes with age.
In humans, stratum corneum hydration increases to a peak level at age 40 years, followed by a decline, especially on the face and neck (Wang et al, 2020).
The reduced stratum corneum hydration in aged skin are due to the reduced content of natural humectants in the skin.
- Hyaluronic acid
- Glycerol
- Filaggrin
- Aquaporin 3
Aging skin has reduced hyaluronic acid
Hyaluronic acid is a substance that occurs naturally in the body and is found in the skin, joints, and connective tissue. Hyaluronic acid is well known as one of the major components of the dermis, and is highly hygroscopic, meaning it can absorb moisture from the air.
Hyaluronic acid provides hydration and structural integrity to the dermis (Verdier-Sévrain et al, 2007).
Aged skin has reduced levels of hyaluronic acid (Oh et al, 2011).
Studies have shown that topical applications of hyaluronic acid can stimulate skin cell differentiation and lipid production, leading to enhancement of epidermal permeability barrier function in both young and aged skin (Bourguignon et al, 2006; Bourguignon et al, 2013).
Aging skin has reduced glycerol
Glycerol is also known as glycerin.
The amount of glycerol in the skin are lower in aged versus young skin (Man et al, 2009; Choi et al, 2005).
Deficiency in glycerol decreases stratum corneum hydration, while topical applications of glycerol improve stratum corneum hydration (Wang et al, 2020).
The beneficial effects of glycerol on the skin have been recognized for over 75 years, and glycerol has been widely used as an ingredient of skincare formulations for its moisturizing and smoothing effects (Fluhr et al, 2008).
Interestingly, it has been shown that glycerol is made by our skin in the pilosebaceous unit and transported through aquaporin 3 (AQP3) channels to the skin.
Endogenous glycerol plays a role in skin hydration, cutaneous elasticity and epidermal barrier repair (Fluhr et al, 2008).
Aging skin has reduced filaggrin
Filaggrin is a protein that is essential for maintaining the integrity of the skin barrier.
Aging skin has reduced levels of filaggrin (Takahashi et al, 2004) and its metabolites, including trans-urocanic acid and pyrrolidone carboxylic acid, which are natural moisturizers in the skin (McAleer et al, 2013).
Aging skin has reduced aquaporin 3
Aquaporins are proteins that increase water movement across the cell membrane.
Aquaporin 3 is the most abundant skin aquaglyceroporin. Both water and glycerol transport by Aquaporin 3 appear to play an important role in hydration of the skin epidermis (Boury-Jamot et al, 2009).
Levels of aquaporin 3 decrease in aged versus young epidermis, leading to reduction in stratum corneum hydration. Aquaporin 3 deficiency-induced reduction in stratum corneum hydration is likely due to decreased glycerol content in the stratum corneum (Wang et al, 2020).
Aging-associated reductions in stratum corneum hydration can be attributed, in large part, to a reduced content of natural moisturizing factors in the epidermis.
How does aging affect the lipid barrier?
With aging, skin becomes dryer and characterized by a lack of brightness of the skin surface, roughness, xerosis, desquamation, and itching, which is related to the decrease in sebum secretion and the reduced levels of epidermal and sebaceous lipids with age (Balin et al, 1989).
Aging skin has reduced epidermal lipids
A report on the biochemical changes of epidermal lipids in the aged skin has shown that the content of three major lipid species, such as ceramide, cholesterol, and fatty acids, was reduced (Ghadially et al, 1995).
Studies have shown that the aged skin barrier (stratum corneum) has a >30% drop in total lipid content in comparison to young stratum corneum (Ghadially et al, 1995), due to reduced epidermal lipid synthesis, particularly in cholesterol synthesis, both under base line conditions and after barrier disruption (Ghadially et al, 1996).
Applying lipid mixtures to skin has been shown to improve epidermal permeability barrier function in aged skin (Zettersten et al, 1997).
Interestingly, studies have shown that either oral or topical administration of ceramides can increase stratum corneum hydration (Bizot et al, 2017; Huang et al, 2008).
Aging skin has reduced fatty acids
Fatty acids are present in the epidermis, especially in the stratum corneum, the outermost layer, and cell membranes.
Skin aging may influence epidermal lipids and free fatty acid composition, and their physiological functions may be involved in aging process (Kim et al, 2010).
Levels of free fatty acids were shown to be significantly lower in older adults (83.7 +/- 9.4 years) compared to younger adults (22.2 +/- 3.9 years) (Hayashi et al, 2003). The composition of linoleic acid (omega 6) decreased in the older group by 40%, suggesting age-dependent loss of oxidatively vulnerable polyunsaturated fatty acid. Furthermore, monounsaturated acids such as palmitoleic and oleic acids decreased significantly in the older group (Hayashi et al, 2003).
In another study, the levels of short chain fatty acids such as palmitic acid and stearic acid, polyunsaturated fatty acids such as linoleic acid (omega 6) and eicosatetraenoic acid were decreased in aged skin by 15%, 31%, 7%, and 56%, compared with those in young skin, respectively. Especially, eicosatetraenoic acid was most significantly decreased in aged skin, indicating that it may relate with intrinsic aging. In contrast, palmitoleic acid and oleic acid were increased in aged skin by 67% and 22%, respectively, compared with those in young skin (Kim et al, 2010).
Lipid antioxidants decrease in the lipid barrier with aging
Lipid antioxidants in the skin barrier include vitamin E, ubiquinone (Coenzyme Q10) and squalene.
The concentration of Vitamin E, ubiquinone and squalene have all been shown to be significantly decreased in aging skin (Passi et al, 2002; Passi et al, 2003).
Vitamin E
Vitamin E is found naturally in your skin barrier.
Vitamin E is the most abundant lipophilic "fat-loving" antioxidant found in human skin (Shindo et al, 1994; Rhie et al, 2001).
Alpha-tocopherol is the main type of vitamin E found in your skin barrier, as well as gamma-tocopherol (Shindo et al, 1994; Thiele et al, 1998).
Vitamin E as alpha-tocopherol was shown to be significantly lower in the skin of older adults compared to younger adults (Passi et al, 2002).
Squalene
Squalene is an oily liquid hydrocarbon. Squalane is its hydrogenated form.
Human sebum naturally contains 13% squalene as one of its major constituents (Kim et al, 2012).
Squalene is a strong antioxidant and is also an emollient and can help the skin maintain hydration.
Levels of squalene in the skin were shown to be significantly lower in older adults compared to younger adults (Passi et al, 2002; Hayashi et al, 2003).
How does aging affect the acid mantle?
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 (Ali et al, 2013; Yosipovitch et al, 1996).
In aged skin, an increased skin surface pH has been repeatedly demonstrated (Choi et al, 2019).
Skin surface pH was significantly higher in an older group of people who were approximately 80 years old, compared with a younger group (Zlotogorski et al, 1987).
A positive correlation between age and skin pH in elderly patients was also reported by Thune et al, 1988.
In a large Chinese cohort, skin surface pH on the forehead of both men and women older than 70 years was higher than in younger groups (Man et al, 2009).
Interestingly, acidification of the stratum corneum has been shown to accelerate barrier recovery in both young and aged skin models (Choi et al, 2007; Hachem et al, 2003; Hachem et al, 2009).
The elevated stratum corneum pH of aged skin likely contributes to the delay in permeability barrier recovery (Wang et al, 2020).
What happens to your skin as you age?
As your body ages, the appearance and characteristics of your skin change.
- Your skin barrier becomes more permeable.
- Reduction in skin hydration.
- Reduction in skin lipids and fats.
- Increase in skin surface pH.
(Choi et al, 2019)
Summary
Aging skin is fragile and is more susceptible to damage.
Skin aging can be caused by internal and external factors.
Intrinsic aging occurs with increasing age and is strongly associated with genetic factors.
Extrinsic aging is caused by exposure to UV radiation (photoaging), air pollution and smoke. Aging is accelerated with exposure to sunlight, air pollution and smoking.
As you age, several changes in your skin occurs.
Your skin barrier becomes weaker, there is a reduction in skin moisture, a reduction in skin lipids, and an increase in skin surface pH levels.
Improvements in epidermal function have been shown to be an effective therapy in the prevention and treatment of some aging-associated skin disorders, including eczema, pruritus, and xerosis.
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Author Information
Dr. Natasha Ryz is a scientist, skin care expert and an entrepreneur. She is the founder of Dry Skin Love Skincare, and she creates skincare products for beauty, dry skin and pain relief.
Dr. Ryz has a PhD in Experimental Medicine from the University of British Columbia in Vancouver, and she is a Vanier scholar. She also holds a Master of Science degree and a Bachelor of Science degree from the University of Manitoba in Winnipeg.
Natasha is the former Chief Science Officer of Zenabis Global, and she oversaw cannabis extraction, analytics, and product development. Her team brought 20 products to market including oils, sprays, vapes and softgels.
Why I Started A Skincare Company