Can eczema leave brown spots?

Brown spots form as a result of melanin accumulation in the skin. This dark brown pigment is essential and plays a protective role against UV rays. However, it can impact the uniformity of the complexion in case of overproduction. The primary cause of brown spots is exposure to the sun's rays: we refer to these as solar spots. Indeed, UV rays act on tyrosine, an amino acid, and, thanks to the enzyme tyrosinase, trigger a cascade of reactions leading to the synthesis of melanin. This process is melanogenesis. That's why it's important to apply sun protection daily. Tobacco and pollution can also contribute to the appearance of brown spots, as these elements generate oxidative stress in the body's cells.

Hyperpigmentation can also be linked to hormonal changes, particularly during pregnancy. Indeed, pregnancy triggers a significant increase in the levels of oestrogen and progesterone in the body, hormones capable of activating melanogenesis. Pigmentation spots related to this phenomenon are referred to as "pregnancy mask". Lastly, brown spots can form following a skin inflammation or lesions. During an inflammation (acne, burn, injury...), pro-inflammatory cytokines stimulate the activity of melanocytes. This is also true in the case of eczema.

Eczema is an inflammatory skin condition characterised by red patches, fine blisters, and scales . The skin in the areas affected by eczema also tends to become rough, eventually presenting crusts and oozing. These various symptoms are accompanied by itching. Eczema is a chronic disease characterised by periods when the lesions worsen, known as eczema flare-ups, and periods of remission. There are several forms of eczema , the most common being atopic eczema, which has a genetic component , and contact eczema, also known as allergic eczema.

It happens that eczema leaves scars, sometimes in the form of brown spots. When the skin is irritated or under the effect of scratching, 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 then activate the protein kinases A and C (PKA and PKC), molecules that allow the phosphorylation and thus the activation of certain proteins involved in melanogenesis. The melanocytes are then stimulated and the synthesis of melanin begins. Post-inflammatory hyperpigmentation is more common in people with dark skin. Indeed, the main form of melanin produced by these people is eumelanin, the darkest form of pigment. This increases the risks of brown spots.

• GOLDENBERG G. & al. Eczema. The Mount Sinai Journal of Medicine (2011).

• BORRADORI L. & al. Dermatologie et infections sexuellement transmissibles. Elsevier Masson (2017).