What is Aging Skin? What Happens to Your Skin as You Age

Posted by Dr. Natasha Ryz on

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? What Happens to Your Skin as You Age

    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.

    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)
      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).

      Learn more: What is Dry Skin? Medical Definitions and References

       What is Aging Skin? What Happens to Your Skin as You Age

      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 Aging Skin? What Happens to Your Skin as You Age

      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 Aging Skin? What Happens to Your Skin as You Age

      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 Aging Skin? What Happens to Your Skin as You Age

      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 Aging Skin? What Happens to Your Skin as You Age

      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).

      Adequate hydration of the stratum corneum serves three major functions (Fowler, 2012):
      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 (Rycroft, 1985).
      The retention of water in the skin is dependent on:
      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). 

      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 Aging Skin? What Happens to Your Skin as You Age

      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 Aging Skin? What Happens to Your Skin as You Age

      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? What Happens to Your Skin as You Age

      How does aging affect the skin barrier?

      As we age, several changes in our skin occur: 

      1. Skin barrier becomes more permeable.
      2. Reduction in skin hydration.
      3. Reduction in skin lipids.
      4. 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).

      What is Aging Skin? What Happens to Your Skin as You Age

      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

      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

      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).

      Aging skin has reduced filaggrin

      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.

      What is Aging Skin? What Happens to Your Skin as You Age

      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).

      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

      The concentration of Vitamin E and ubiquinone (Coenzyme Q10), which together with squalene, play a key role against external oxidative insult, has been shown to decrease significantly in aging skin (Passi et al, 2003). 

       What is Aging Skin? What Happens to Your Skin as You Age

      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 is Aging Skin? What Happens to Your Skin as You Age

      What happens to your skin as you age?

      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)

      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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      What Happens to Your Skin as You Age?

      References

      Ali SM, Yosipovitch G. Skin pH: from basic science to basic skin care. Acta Derm Venereol 2013; 93: 261–267. 

      Ananthapadmanabhan KP, Mukherjee S, Chandar P. Stratum corneum fatty acids: their critical role in preserving barrier integrity during cleansing. Int J Cosmet Sci. 2013 Aug;35(4):337-45. 

      Balin A. K., Pratt L. A. (1989). Physiological consequences of human skin agingCutis 43 (5), 431–436. 

      Bizot V, Cestone E, Michelotti A, Nobile V. Improving Skin Hydration and Age-related Symptoms by Oral Administration of Wheat Glucosylceramides and Digalactosyl Diglycerides: A Human Clinical Study. Cosmetics. 2017; 4:37.

      Bocheva G, Slominski RM, Slominski AT. The Impact of Vitamin D on Skin Aging. Int J Mol Sci. 2021 Aug 23;22(16):9097. 

      Bourguignon LY, Ramez M, Gilad E, Singleton PA, Man MQ, Crumrine DA, Elias PM, Feingold KR. Hyaluronan CD44 interaction stimulates keratinocyte differentiation, lamellar body formation/secretion, and permeability barrier homeostasis. J Invest Dermatol. 2006; 126:1356–65. 

      Bourguignon LY, Wong G, Xia W, Man MQ, Holleran WM, Elias PM. Selective matrix (hyaluronan) interaction with CD44 and RhoGTPase signaling promotes keratinocyte functions and overcomes age related epidermal dysfunction. J Dermatol Sci. 2013; 72:32–44. 

      Boury-Jamot M, Daraspe J, Bonté F, Perrier E, Schnebert S, Dumas M, Verbavatz JM. Skin aquaporins: function in hydration, wound healing, and skin epidermis homeostasis. Handb Exp Pharmacol. 2009;(190):205-17.

      Caspers PJ, Lucassen GW, Carter EA et al. In vivo confocal Raman microspectroscopy of the skin: noninvasive determination of molecular concentration profiles. J Invest Dermatol 2001; 116:434– 42.

      Caspers PJ, Lucassen GW, Puppels GJ. Combined in vivo confocal Raman spectroscopy and confocal microscopy of human skin. Biophys J 2003 July; 85: 572-80.

      Choi EH, Man MQ, Wang F, Zhang X, Brown BE, Feingold KR, Elias PM. Is endogenous glycerol a determinant of stratum corneum hydration in humans? J Invest Dermatol. 2005; 125:288–93.

      Choi EH. Aging of the skin barrier. Clin Dermatol. 2019 Jul-Aug;37(4):336-345.

      Choi EH, Man MQ, Xu P, Xin S, Liu Z, Crumrine DA, Jiang YJ, Fluhr JW, Feingold KR, Elias PM, Mauro TM. Stratum corneum acidification is impaired in moderately aged human and murine skin. J Invest Dermatol. 2007; 127:2847–56.
       
      Chung JH, Hanft VN, Kang S. Aging and photoaging. J Am Acad Dermatol 2003;49:690-697.

      Dikstein S, Zlotogorski A: Measurements of skin pH. Acta Derm Venereol (Stockh) 1994;(suppl 185):18–20.

      Farage MA, Miller KW, Berardesca E, Maibach HI. Clinical implications of aging skin: cutaneous disorders in the elderly. Am J Clin Dermatol. 2009;10(2):73-86.

      Fisher GJ, Kang S, Varani J, et al. Mechanisms of photoaging and chronological skin aging. Arch Dermatol 2002;138:1462-1470. 

      Fowler J. Understanding the Role of Natural Moisturizing Factor in Skin Hydration. Practical Dermatology. 2012; July. 36-40.

      Ghadially R, Brown BE, Sequeira-Martin SM, Feingold KR, Elias PM. The aged epidermal permeability barrier. Structural, functional, and lipid biochemical abnormalities in humans and a senescent murine model. J Clin Invest. 1995; 95:2281–90.

      Ghadially R, Brown BE, Hanley K, Reed JT, Feingold KR, Elias PM. Decreased epidermal lipid synthesis accounts for altered barrier function in aged mice. J Invest Dermatol. 1996; 106:1064–69.

      Hachem JP, Roelandt T, Schürer N, Pu X, Fluhr J, Giddelo C, Man MQ, Crumrine D, Roseeuw D, Feingold KR, Mauro T, Elias PM. Acute acidification of stratum corneum membrane domains using polyhydroxyl acids improves lipid processing and inhibits degradation of corneodesmosomes. J Invest Dermatol. 2010; 130:500–10. https://doi.org/10.1038/jid.2009.249 PMID:19741713 37.

      Hachem JP, Crumrine D, Fluhr J, Brown BE, Feingold KR, Elias PM. pH directly regulates epidermal permeability barrier homeostasis, and stratum corneum integrity/cohesion. J Invest Dermatol. 2003; 121:345–53.

      Huang HC, Chang TM. Ceramide 1 and ceramide 3 act synergistically on skin hydration and the transepidermal water loss of sodium lauryl sulfate irritated skin. Int J Dermatol. 2008; 47:812–19. 

      Imokawa G, Abe A, Jin K, Higaki Y, Kawashima M, Hidano A. Decreased level of ceramides in stratum corneum of atopic dermatitis: an etiologic factor in atopic dry skin? J Invest Dermatol. 1991; 96:523–26.

      Jenkins G. Molecular mechanisms of skin ageing. Mech Ageing Dev. 2002;123:801–810.

      Jin SP, Han SB, Kim YK, et al. Changes in tight junction protein expression in intrinsic aging and photoaging in human skin in vivo. J Dermatol Sci 2016;84:99-101.

      Kim EJ, Kim MK, Jin XJ, Oh JH, Kim JE, Chung JH. Skin aging and photoaging alter fatty acids composition, including 11,14,17-eicosatrienoic acid, in the epidermis of human skin. J Korean Med Sci. 2010 Jun;25(6):980-3.

      Kim EJ, Jin XJ, Kim YK, Oh IK, Kim JE, Park CH, Chung JH. UV decreases the synthesis of free fatty acids and triglycerides in the epidermis of human skin in vivo, contributing to development of skin photoaging. J Dermatol Sci. 2010 Jan;57(1):19-26.

      Lambers H, Piessens S, Bloem A, Pronk H, Finkel P. Natural skin surface pH is on average below 5, which is beneficial for its resident flora. Int J Cosmet Sci 2006; 28: 359–370.

      Man MQ, Xin SJ, Song SP, Cho SY, Zhang XJ, Tu CX, Feingold KR, Elias PM. Variation of skin surface pH, sebum content and stratum corneum hydration with age and gender in a large Chinese population. Skin Pharmacol Physiol. 2009; 22:190–99.

      McAleer MA, Irvine AD. The multifunctional role of filaggrin in allergic skin disease. J Allergy Clin Immunol. 2013; 131:280–91.

      Milstone LM. Epidermal desquamation. J Dermatol Sci. 2004 Dec;36(3):131-40.

      Oh JH, Kim YK, Jung JY, Shin JE, Chung JH. Changes in glycosaminoglycans and related proteoglycans in intrinsically aged human skin in vivo. Exp Dermatol. 2011; 20:454–56. 

      Pappas A. Epidermal surface lipids. Dermatoendocrinol. 2009 Mar;1(2):72-6.

      Passi S, De Pità O, Grandinetti M, Simotti C, Littarru GP. The combined use of oral and topical lipophilic antioxidants increases their levels both in sebum and stratum corneum. Biofactors. 2003;18(1-4):289-97.  

      Rycroft RJ. Low humidity and microtrauma. Am J Ind Med 1985; 8:371–3.

      Schade H, Marchionini A. Der s€auremantel der haut (nach Gaskettenmessung). Klin Wochenschr 1928; 7: 12–14. 

      Schmid-Wendtner MH, Korting HC. The pH of the skin surface and its impact on the barrier function. Skin Pharmacol Physiol. 2006;19(6):296-302.

      Takahashi M, Tezuka T. The content of free amino acids in the stratum corneum is increased in senile xerosis. Arch Dermatol Res. 2004; 295:448–52.

      Tagami H. Functional characteristics of the stratum corneum in photoaged skin in comparison with those found in intrinsic aging. Arch Dermatol Res. 2008 Apr;300 Suppl 1:S1-6.

      Thune P, Nilsen T, Hanstad IK, et al. The water barrier function of the skin in relation to the water content of stratum corneum, pH and skin lipids. The effect of alkaline soap and syndet on dry skin in elderly, non-atopic patients. Acta Derm Venereol 1988;68:277-283.

      Verdier-Sévrain S, Bonté F. Skin hydration: a review on its molecular mechanisms. J Cosmet Dermatol. 2007 Jun;6(2):75-82.

      Wang Z, Man MQ, Li T, Elias PM, Mauro TM. Aging-associated alterations in epidermal function and their clinical significance. Aging (Albany NY). 2020 Mar 27;12(6):5551-5565.

      Warner RR, Myers MC, Taylor DA. Electron probe analysis of human skin: determination of the water concentration profile. J Invest Dermatol 1988; 90: 218–24.

      White MW, Karam S, Cowell B. Skin tears in frail elders: a practical approach to prevention. Geriatr Nurs. 1994;15(2):95-99.

      White-Chu EF, Reddy M. Dry skin in the elderly: complexities of a common problem. Clin Dermatol. 2011 Jan-Feb;29(1):37-42.

      Yosipovitch G, Maibach HI. Skin surface pH: a protective acid mantle. Cosmet Toiletries 1996; 111: 101–112. 

      Zettersten EM, Ghadially R, Feingold KR, Crumrine D, Elias PM. Optimal ratios of topical stratum corneum lipids improve barrier recovery in chronologically aged skin. J Am Acad Dermatol. 1997; 37:403–08.

      Zlotogorski A. Distribution of skin surface pH on the forehead and cheek of adults. Arch Dermatol Res 1987;279:398-401. 

      Aging Skin Dry Skin

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