How does eczema present itself on black skin?

It is generally considered that the symptoms of eczema are similar regardless of skin colour. However, this is not entirely true. While the sensations of itching, blisters and scales are indeed present in all skin tones, the colour of the lesions slightly differs. Indeed, on darker skin, the rashes tend to take on brown or grey hues. Thus, eczema lesions appear darker than the rest of the body. This is even more pronounced when the eczema is at the stage of lichenification, that is, when the skin becomes rough and thickens.

It sometimes happens that eczematous lesions leave brown spots after their healing, partly due to scratching. This phenomenon is particularly common in individuals with black skin. Indeed, when the skin is irritated, it triggers an inflammatory response, resulting in the release of pro-inflammatory cytokines such as interleukin-1 (IL-1) and tumour necrosis factor (TNF-α). These cytokines cause the activation of melanocytes, cells in the basal layer of the epidermis responsible for synthesising melanin, the pigment that gives skin its colour. In individuals with black skin, the melanin produced is darker, referred to as eumelanin, which increases the risks of hyperpigmentation.

Finally, it's worth noting that many individuals with darker skin express concerns about the risk ofhypopigmentation following the use of dermocorticoids. It is true that when used excessively, these cortisone creams can cause hypopigmentation. However, when they are applied following dermatological advice, which is once a day on lesions and only during eczema flare-ups, the risks are very limited. Moreover, dermocorticoids are highly effective and have recognised anti-inflammatory and anti-itching effects. Considering the risks of hyperpigmentation caused by scratching, the benefit-risk balance tends to lean towards the use of cortisone creams.

The causes of eczema are broadly the same regardless of the skin colour it affects. This condition arises from a defect in the skin barrier or an allergy to a specific substance. However, some studies have looked at the prevalence and etiology of eczema according to skin tones and have made several interesting discoveries. In the United States, ethnic statistics have revealed that the prevalence of eczema is about 20% in children with dark skin compared to 15% in children with light skin. This difference is currently unexplained. However, scientists have highlighted that the genetic mutations responsible for eczema are not always the same depending on the skin tone.

mutations on this gene are about six times less common in people with black skin suffering from eczema than in people with white skin. Eczema in the former is more often the result of a mutation on the gene coding for filaggrin-2, fulfilling a role similar to that of filaggrin, which explains why the biological mechanisms of eczema are generally similar across all skin tones. Finally, people with dark skin affected by eczema more frequently present a mutation of the gene coding for claudin than people with light skin. This protein contributes to the formation of tight junctions, controlling the seal between two cellular compartments.

In conclusion, the etiological differences in eczema according to skin tones are minimal and do not lead to vastly dissimilar disease manifestations. These differences can be explained by a relatively low level of intermixing between individuals of different skin colours, leading to the reproduction and compartmentalisation of genes within the same communities.