Racial/Ethnic Variations in Skin Barrier: Implications for Skin Care Recommendations in Skin of Color

September 2021 | Volume 20 | Issue 9 | Original Article | 932 | Copyright © September 2021

Published online August 31, 2021

Andrew F. Alexis MD MPHa*, Heather Woolery-Lloyd MD FAADb*, Kiyanna Williams MD FAADc, Anneke Andriessen PhDd, Seemal Desai MD FAADe, George Han MD FAADf, Maritza Perez MD FAADg, Wendy Roberts MD FAADh, Susan Taylor MD FAADi

aWeill Cornell Medicine, New York, NY
bSkin of Color Division, Dr Phillip Frost Department of Dermatology and Cutaneous Surgery, University of Miami, Miller School of Medicine, FL
cSkin of Color Section, Department of Dermatology, Cleveland Clinic, Cleveland, OH
dRadboud UMC Nijmegen, Andriessen Consultants, Malden, NL
eDepartment of Dermatology, The University of Texas Southwestern Medical Center, Innovative Dermatology, PA, Dallas, TX
fDepartment of Dermatology, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell, New York, NY
gDepartment of Dermatology, University of Connecticut School of Medicine New Canaan, CT
hGeneral and Cosmetic Dermatology, Rancho Mirage, CA
iSandra J Lazarus, Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA Wynnewood, PA

*co-first authors

Black and White patients at multiple anatomical sites.12 Taken together, the available data support structural and functional variations in the stratum corneum between populations, but these vary by anatomic location or methodology, and therefore, may not be generalizable to the diverse range of populations with skin of color (Table 1).

Skin Barrier: pH
Physiological skin surface pH is acidic (4–6), while the body's internal pH is neutral to slightly alkaline (~7.4).13-15 Buffer capacity results from free fatty acids and components of natural moisturizing factors (NMF) urocanic acid, carbonic acid, and keratins.14 Skin surface pH influences skin barrier homeostasis, SC integrity and cohesion, and antimicrobial defense mechanisms. In inflammatory skin diseases, such as atopic dermatitis (AD) and acne, skin surface pH is elevated, and therapeutic measures, alkaline cleansers, and moisturizers may deteriorate the condition.16 An alkaline skin surface pH leads to disruptions in the skin's acid mantle and may influence skin barrier function.

Few studies have examined pH in skin of color.13-15 One study demonstrated decreased pH in Black skin after three tape strips but not at baseline or after subsequent tape strips.14 In contrast, a study of South African nursing students showed increased skin surface pH in Black subjects compared to White subjects.15 Another study revealed no difference in skin surface pH between Black and White subjects.13 Thus, the data from these three studies are insufficient to draw any definitive conclusions on pH in skin of color.

2. Skin barrier differences between racial/ethnic populations may contribute to variations in the prevalence and severity of atopic dermatitis, xerosis, and pruritus.

Variations in the prevalence of AD in different racial/ethnic populations have been reported. Several studies have shown a higher prevalence of AD in Black children compared to White children.16-18 Greater severity of AD in Black children compared to White children was reported in one study after adjusting the erythema score in the Score Atopic Dermatitis index (SCORAD).19,20 Prevalence and impact of pruritus have also been greater in Blacks than White populations.20-22 In a cross-sectional study of a middle-aged and elderly population, skin pigmentation (as well as age, female sex, body mass index, outside temperature, eczema, and chemotherapy) were significant determinants for both generalized and localized dry skin. Individuals with Brown-Black skin color were more likely to have generalized dry skin than the reference group of olive to light brown skin color.23

Causative factors for observed differences in prevalence and severity of AD, xerosis, and pruritus published in the literature remain unclear, although the aforementioned skin barrier differences mentioned above may be contributory. The role of genetic factors (including those related to barrier structure and