Dry Skin in Africans: Understanding Our Skin's Unique Factors

My mom would send me back into the house, to apply more lotion on my body because I looked “ashy” and would ensure that I was well-greased before leaving the house for school. I am so glad my ‘ashy’ days are over because I understand my dry skin as an African, and so will you. 

I want to ask if you’ve ever used body lotion pumps in a day, and yet you continue to struggle with flaky, tight, and possibly itchy skin. If yes, this post will explore the distinct characteristics of African skin and kick-start your journey to radiant skin.

The cause of reported differences in the prevalence and severity of atopic dermatitis, xerosis, and pruritus in Africans, compared to other racial groups is our unique skin barrier composition and our rich skin pigmentation

The skin barrier is the outermost layer of the skin, also known as the stratum corneum. The stratum corneum is the surface layer of the epidermis of our skin. 

According to Murphrey et al., in 2023, they defined the stratum corneum as the first line of defense for the body, serving an essential role as a protective skin barrier against the external environment. The stratum corneum aids in hydration and water retention, which prevents cracking of the skin.

In simpler terms, the skin barrier or stratum corneum is your waterproof barrier, keeping out microbes like bacteria, fungi and viruses. It also protects your insides from harm. This layer is thicker in areas like your palms and feet that need extra protection.

The stratum corneum is made up of 20-30 cell layers and based on a study carried out by Muizzuddin et al., in 2010, black skin was reported to have a greater number of cell layers arranged more compactly, resulting in a stronger stratum corneum barrier function and faster recovery from barrier damage. 

Also, present in the stratum corneum are corneocytes embedded in a lipid matrix. The stratum corneum structure is frequently described as having a "brick-and-mortar" structure, with the lipids serving as the mortar and the corneocytes acting as the bricks. The stratum corneum lipids act to defend the skin from foreign bodies and promote moisture retention. 

In 2021, Alexis et al. stated that the stratum corneum lipids comprise approximately 20% of the volume of the stratum corneum and are composed of ceramides (40-50%), cholesterol (25%) and free fatty acids (10-15%). Perfect barrier function in the stratum corneum depends on having an optimal lipid content.

Although several studies have reported that black skins have greater overall lipid content, more studies have shown that ceramide levels are lowest in black skin. Ceramide comprises approximately 50% of the stratum corneum lipid content and is crucial for forming and preserving the skin's water permeability barrier function. 

One major factor influencing the skin's surface suppleness is water found in the stratum corneum. Water typically makes up 10%–30% of the stratum corneum. Both the permeability barrier and the stratum corneum's capacity to retain water control this water content.

The skin may seem dry and lose its suppleness when the water content falls below 10% because of sickness or environmental changes. Wan et al., in 2014 reported that black skin had the lowest water content, compared to other racial groups, in its stratum corneum, resulting in lower skin hydration in black skin. 

Transepidermal water loss (TEWL) is the amount of water vapour passively evaporating from the surface of the skin. In healthy skin, TEWL is directly proportional to skin hydration. The ratio of TEWL to skin hydration is inverse in many skin illnesses (e.g., increased TEWL with decreased skin hydration, as found in atopic dermatitis).

The amount of insensible skin water loss (TEWL) is a commonly used indicator of skin barrier function. Trans-epidermal water loss in African American skin was shown to be greater, as noted by Wan et al, in 2014. 

Ceramide levels are inversely correlated with trans-epidermal water loss and directly correlated with the water content of the stratum corneum. Abnormalities in ceramide composition alter the stratum corneum’s physiologic properties and contribute to barrier dysfunction and disease. Hence, reduced levels of ceramide in black skin have implications for the presence of xerosis.

The stratum corneum's surface pH is extremely acidic, which has antimicrobial properties, controls permeability barrier homeostasis, and preserves the integrity and cohesiveness of the stratum corneum (desquamation). The presence of melanin also affected the skin's surface pH. 

In 2009, Gunathilake et al. reported that the surface pH of deep melanated skin was lower than lighter skin, which correlates with superior barrier function or stratum corneum integrity in darkly pigmented skin, independent of ethnicity, age, gender, season, and latitude. Deeply melanated skins also showed significantly superior permeability function because of faster barrier recovery rates after acute barrier disruption. 

Furthermore, melanocytes were found to have an impact on epidermal function. The study revealed that melanocytes with darker pigmentation exhibit a lower pH, and their dendrites display vesicular organelles that may be related to melanosomes.

The degree of melanization is inversely associated with the pH of melanosomes, which are acidic organelles according to earlier research. Melanocytes produce melanosomes. Melanosomes are organelles that function to synthesize/produce and store melanin. 

Moreover, darkly pigmented melanocytes release more melanosomes into the outside epidermis, which may explain the pH difference between lightly and darkly pigmented individuals. Thus, the transfer of more acidified organelles from the melanocytic dendrites could explain, at least in part, the lower pH of the stratum corneum in darkly pigmented individuals.

In contrast, skin hydration was significantly lower and skin surface pH was significantly higher in South African nursing students when compared to Caucasian nursing students, as reported by Young et al., in 2019.

More studies have been carried out on determining the pH of pigmented individuals, but there has been varying and insufficient data, to draw any definitive conclusions on pH in pigmented skin. 

In Africa, we need to do more comprehensive clinical trials and investigative research tailored to our demographic and environment to better inform optimal skincare advice and regimens for the diverse African population. 

In the African community, dry skin can be culturally stigmatizing, dry skin on a dark skin gives a grey or ashen appearance and is often referred to as “ashy skin”. Because of its physical look, dry skin is more evident on African skin and has greater cultural value. Daily moisturization is regarded as a cultural standard in the personal care routines of Africans. 

REFERENCES

Alexis, A., Woolery-Lloyd, H., Williams, K., Andriessen, A., Desai, S., Han, G., Perez, M., Roberts, W., & Taylor, S. (2021). Racial/Ethnic Variations in Skin Barrier: Implications for Skin Care Recommendations in Skin of Color. Journal of Drugs in Dermatology, 20(9), 932–938. https://doi.org/10.36849/JDD.6312

Gunathilake, R., Schurer, N. Y., Shoo, B. A., Celli, A., Hachem, J.-P., Crumrine, D., Sirimanna, G., Feingold, K. R., Mauro, T. M., & Elias, P. M. (2009). pH-Regulated Mechanisms Account for Pigment-Type Differences in Epidermal Barrier Function. Journal of Investigative Dermatology, 129(7), 1719–1729. https://doi.org/10.1038/jid.2008.442

Muizzuddin, N., Hellemans, L., Van Overloop, L., Corstjens, H., Declercq, L., & Maes, D. (2010). Structural and functional differences in barrier properties of African American, Caucasian and East Asian skin. Journal of Dermatological Science, 59(2), 123–128. https://doi.org/10.1016/j.jdermsci.2010.06.003

Murphrey, M. B., Miao, J. H., & Zito, P. M. (2023). Histology, Stratum Corneum. In StatPearls. StatPearls Publishing. http://www.ncbi.nlm.nih.gov/books/NBK513299/

Wan, D. C., Wong, V. W., Longaker, M. T., Yang, G. P., & Wei, F.-C. (2014). Moisturizing Different Racial Skin Types. The Journal of Clinical and Aesthetic Dermatology, 7(6), 25–32.