Dark skin is voluminous and rich in collagen, on the other hand, unique problems concerning scarring and pigmentation are more likely to arise. Special consideration is necessary to account for the unique structural and functional differences between dark and light skin.
The keyword is Melanin! Melanin is a natural pigment found in the body and is produced within a specialized group of cells known as melanocytes. These cells “pack” the pigment in “bags”, so called melanosomes, which are then transported to the keratinocytes, the cells that make up the superficial layer of our skin. The number, size, and shape of melanosomes are genetically determined, and ethnically dark-skinned individuals have not only more melanosomes, but they are also larger and more oval than melanosomes in Caucasians. The average number of melanocytes, however, remains the same among both ethnic groups (1).
Dispersed melanosomes absorb light better, so that the skin appears darker. Melanin is most dense in the lower cell layers of the epidermis, the superficial layer of the skin, and in the upper ones it undergoes enzymatic degradation. In dark skinned individuals, melanin residues are still detectable in the stratum corneum, the outermost skin layer. In Caucasians, this finding is seen only in pathological conditions (2).
Although dark skin provides protection from the effects of UV radiation (3), such as skin cancer and photoaging, it is more vulnerable to dyspigmentation. Hypo- and hyperpigmentation are signs of photoaging in people with dark skin. This is why skin of color should only be treated with gentle cosmetic products.
Any alterations of the skin barrier function may lead to inflammation and thus cause a condition known as post-inflammatory hyperpigmentation, which is difficult to treat.
Signs of aging include loss of volume and elasticity and the appearance of wrinkles. The middle layer of the skin, or dermis, is thicker in black skin than white, and the thickness is proportional to the amount of pigmentation. It also contains more fibroblasts, which synthesize collagen, among other proteins, and play a critical role in wound healing (4).
Due to these unique characteristics of dark skin, it tends to show signs of aging at a slower rate than seen in Caucasians. However, as part of the aging process in all individuals, the life span of fibroblasts is reduced and their potential for cell division decreases in the elderly. Diminished fibroblast functionality and reactivity likely contribute to both the aging process and abnormal scarring.