Dermatological Conditions in Skin of Color— Physiological Nuances in Skin of Color and Their Clinical Implications

 J Clin Aesthet Dermatol. 2023;16(2 Suppl 1):S12–S13

by Archana M. Sangha, MMS, PA-C 

Ms. Sangha is a medical science liaison for Incyte in Wilmington, Delaware. Prior to that, she spent over a decade as a dermatology PA specializing in general, surgical, and cosmetic dermatology. She is a fellow of the American Academy of Physician Assistants in Alexandria, Virginia. She is also Immediate Past President of the Society of Dermatology Physician Assistants.

FUNDING: No funding was provided for this article.

DISCLOSURES: Ms. Sangha is an employee of Incyte in Wilmington, Delaware. 

Numerous studies have suggested that there are subtle physiological variances in the skin depending on a patient’s ethnic background. While larger studies need to be performed, there are certain trends of differences observed among the varying skin types. This article will look at five nuances seen in skin of color (SOC). 

Vitamin D levels 

SOC patients are at higher risk of vitamin D deficiency. Vitamin D plays an important role in calcium homeostasis and bone metabolism.¹ In the skin, it regulates numerous processes ranging from cellular proliferation and differentiation to barrier maintenance and immune functions. Vitamin D deficiency has been associated with increased risk of psoriasis and atopic dermatitis.² The skin is the site of vitamin D synthesis. When exposed to ultraviolet radiation, provitamin D3 is pholysed to previtamin D3.³ This photolysation happens at a lower rate in SOC patients due to their increased levels of melanin, compared to lighter skin types, thus placing this population at increased risk of vitamin D deficiency.¹ 

Ceramide Levels 

Ceramides are the major lipid constituent found within the lamellar sheets in the stratum corneum. Ceramides play an important role in the barrier function of the skin.⁴ A study by Sugino et al⁵ found that Asian skin has the highest ceramide levels, followed by Caucasian skin and then Black skin. Ceramide levels are inversely correlated with transepidermal water loss (TEWL), and skin disorders with a compromised barrier function, such as atopic dermatitis and psoriasis, have lower total ceramide content.⁴

Skin reactivity 

Erythema has been commonly used as a marker for skin sensitivity. In SOC populations, erythema is more difficult to detect. To be more objective, studies now employ the use of Doppler velocimetry. This device noninvasively measures the number of red blood cells times their velocity, thus conveying information regarding blood flow changes.⁶ A vasodilator, such as methyl nicotinate, is applied to the skin and then blood flow is measured and compared to baseline.⁷ Skin that vasodilates the fastest is found to be the most reactive. Several studies have found Asian skin to be the most reactive, followed by Caucasian skin and then Black skin.^8,9

TEWL 

TEWL is a measure of the water vapor evaporating from the skin surface. It is an important indicator of skin barrier function. Several studies have been done comparing TEWL in different ethnic groups. One study by Muizzuddin et al¹⁰ looked at TEWL on the face and found that African Americans had lower TEWL values compared too East Asians. In a study by Wilson et al,¹¹ investigators compared TEWL at different body locations in African American women and White women. TEWL was similar among both groups when measured on the forearm; however, African American women had lower TEWL in cheeks and legs.¹¹ Several other studies have been performed comparing TEWL in Black and White skin and the results have been contradictory; thus, no definitive conclusions can be made at this time. More robust and diverse research is needed.

Sebum content  

In a study by Rawlings,¹² Black patients were found to have 60 to 70 percent more lipid content in their hair than Caucasian patients. Another study looking at pores and sebum in multi-ethnic female populations found that despite ethnicity, the number of pores increased with age.¹³ African American patients had the highest sebum production, followed by East Asians, Caucasians, and then Hispanics. These findings may influence your choices of vehicle bases, choosing more emollient based vehicles for those with less sebum production and vice versa.

In Closing

Being aware of these physiological variances in SOC can help inform some of your treatment recommendations. For example, if performing a chemical peel on a patient, it would be prudent to not only take into account their medical history but also their ethnicity. Based on studies by Gean et al⁸ and Kompore et al,⁹ you can anticipate that Asian skin will be more reactive than Black skin. There is a need for larger and more robust multi-ethnic studies to more comprehensively understand the physiological variances in SOC and how these variances may impact patient care.

References

1. Sizar O, Khare S, Goyal A, Givler A. Vitamin D deficiency. 2022 Jul 27. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan–. PMID: 30335299.
2. Umar M, Sastry KS, Al Ali F, et al. Vitamin D and the pathophysiology of inflammatory skin diseases. Skin Pharmacol Physiol. 2018;31(2):74-86. doi: 10.1159/000485132. Epub 2018 Jan 6. 
3. Holick MF, Smith E, Pincus S. Skin as the site of vitamin D synthesis and target tissue for 1,25-dihydroxyvitamin D3: use of calcitriol (1,25-dihydroxyvitamin D3) for treatment of psoriasis. Arch Dermatol. 1987 Dec;123(12):1677-1683a.
4. Coderch L, López O, de la Maza A, Parra JL. Ceramides and skin function. Am J Clin Dermatol. 2003;4(2):107-29. doi: 10.2165/00128071-200304020-00004. 
5. Sugino K, Imokawa G, Maibach HI. Ethnic difference of stratum corneum lipid in relation to stratum corneum function. J Invest Dermatol. 1993;100(4):587.
6. Ewald U, Huch A, Huch R, Rooth G. Skin reactive hyperemia recorded by a combined TcPO2 and laser Doppler sensor. Adv Exp Med Biol. 1987;220:231-4. doi: 10.1007/978-1-4613-1927-6_42. 
7. Berardesca E, Maibach HI. Racial differences in sodium lauryl sulphate induced cutaneous irritation: black and white. Contact Dermatitis. 1988;18(2):65–70.
8. Gean CJ, Tur E, Maibach HI, Guy RH. Cutaneous responses to topical methyl nicotinate in black, oriental, and caucasian subjects. Arch Dermatol Res. 1989;281(2):95–98.
9. Kompaore F, Marty JP, Dupont C. In-vivo evaluation of the stratum corneum barrier function in Blacks, Caucasians, and Asians with two noninvasive methods. Skin Pharmacol. 1993;6(3):200–207.
10. Muizzuddin N, et al. Structural and functional differences in barrier properties of African American, Caucasian and East Asian skin. J. Dermatol. Sci. 2010;59:123–128.
11. Wilson D, Berardesca E, Maibach HI. In vitro transepidermal water loss: differences between black and white human skin. Br J Dermatol. 1988 Nov;119(5):647-52
12. Rawlings AV. Ethnic skin types: are there differences in skin structure and function? J Cosmet Sci. 2006;28(2):79–93.
13. Hillebrand GG, Levine MJ, Miyamoto K. The age dependent changes in skin condition in African Americans, Asian Indians, Caucasians, East Asians, and Latinos. IFSCC J 2001;4:259–266.