Atopic dermatitis (AD) is a chronic inflammatory disorder that affects individuals worldwide.1 Although AD previously was commonly described as a skin-limited disease of childhood characterized by eczema in the flexural folds and pruritus, our current understanding supports a more heterogeneous condition.2 We review the wide range of cutaneous presentations of AD with a focus on clinical and morphological presentations across diverse skin types—commonly referred to as skin of color (SOC).
Defining SOC in Relation to AD
The terms SOC, race, and ethnicity are used interchangeably, but their true meanings are distinct. Traditionally, race has been defined as a biological concept, grouping cohorts of individuals with a large degree of shared ancestry and genetic similarities,3 and ethnicity as a social construct, grouping individuals with common racial, national, tribal, religious, linguistic, or cultural backgrounds.4 In practice, both concepts can broadly be envisioned as mixed social, political, and economic constructs, as no one gene or biologic characteristic distinguishes one racial or ethnic group from another.5
The US Census Bureau recognizes 5 racial groupings: White, Black or African American, American Indian or Alaska Native, Asian, and Native Hawaiian or other Pacific Islander.6 Hispanic or Latinx origin is considered an ethnicity. It is important to note the limitations of these labels, as they do not completely encapsulate the heterogeneity of the US population. Overgeneralization of racial and ethnic categories may dull or obscure true differences among populations.7
From an evolutionary perspective, skin pigmentation represents the product of 2 opposing clines produced by natural selection in response to both need for and protection from UV radiation across lattitudes.8 Defining SOC is not quite as simple. Skin of color often is equated with certain racial/ethnic groups, or even binary categories of Black vs non-Black or White vs non-White. Others may use the Fitzpatrick scale to discuss SOC, though this scale was originally created to measure the response of skin to UVA radiation exposure.9 The reality is that SOC is a complex term that cannot simply be defined by a certain group of skin tones, races, ethnicities, and/or Fitzpatrick skin types. With this in mind, SOC in the context of this article will often refer to non-White individuals based on the investigators’ terminology, but this definition is not all-encompassing.
Historically in medicine, racial/ethnic differences in outcomes have been equated to differences in biology/genetics without consideration of many external factors.10 The effects of racism, economic stability, health care access, environment, and education quality rarely are discussed, though they have a major impact on health and may better define associations with race or an SOC population. A discussion of the structural and social determinants of health contributing to disease outcomes should accompany any race-based guidelines to prevent inaccurately pathologizing race or SOC.10
Within the scope of AD, social determinants of health play an important role in contributing to disease morbidity. Environmental factors, including tobacco smoke, climate, pollutants, water hardness, und urban living, are related to AD prevalence and severity.11 Higher socioeconomic status is associated with increased AD rates,12 yet lower socioeconomic status is associated with more severe disease.13 Barriers to health care access and suboptimal care drive worse AD outcomes.14 Underrepresentation in clinical trials prevents the generalizability and safety of AD treatments.15 Disparities in these health determinants associated with AD likely are among the most important drivers of observed differences in disease presentation, severity, burden, and even prevalence—more so than genetics or ancestry alone16—yet this relationship is poorly understood and often presented as a consequence of race. It is critical to redefine the narrative when considering the heterogeneous presentations of AD in patients with SOC and acknowledge the limitations of current terminology when attempting to capture clinical diversity in AD, including in this review, where published findings often are limited by race-based analysis.
Epidemiology
The prevalence of AD has been increasing over the last few decades, and rates vary by region. In the United States, the prevalence of childhood and adult AD is 13% and 7%, respectively.17,18 Globally, higher rates of pediatric AD are seen in Africa, Oceania, Southeast Asia (SEA), and Latin America compared to South Asia, Northern Europe, and Eastern Europe.19 The prevalence of AD varies widely within the same continent and country; for example, throughout Africa, prevalence was found to be anywhere between 4.7% and 23.3%.20