Problems In Treating Darker Skin

The most apparent problem in treating darker skin types is the amount of epidermal melanin present. This melanin acts as a competing chromophore for the laser or light energy. If a significant amount of energy is absorbed by the epidermal melanin, acute problems such as blistering and crusting, as well as long term complications such as scarring and dyspigmentation, may occur. Melanosomes in black skin are not only increased in number compared to white skin, but are distributed throughout the entire epidermis, including the stratum basale, granulosum, lucidum, and corneum. The melanosomes are larger, individually dispersed, and have a higher melanin content than the smaller, aggregated melanosomes with less melanin found in white non-tanned skin. These melanosomes are able to absorb more light and therefore less light reaches the intended chromophore within the hair follicle, making the procedure essentially ineffective. As mentioned above, the majority of black patients have spiral shaped hair and the follicles themselves are curved. Together, this makes black patients more prone to the condition of pseudofolliculitis barbae. Other differences in hair follicles have been studied, and perhaps not surprisingly, black hair is more heavily pigmented compared to white hair. Melanosomes are present in both the outer root sheath and in the bulb of vellus hairs in black patients, but not in white patients. The total hair density and total number of terminal hair follicles is significantly lower in African Americans compared with white subjects.14 This is particularly important in hair removal, as a higher density of hair follicles leads to more thermal energy absorption and therefore a greater risk for adverse effects. Although studies assessing the thickness of the epidermis and dermis find no difference between white and black skin,15 there is a difference in composition of the dermis. Fibroblasts are larger and increased in number compared to white skin. The collagen fiber bundles are smaller and more closely stacked in black skin. Although we are unsure of the importance of these findings, there may be some contribution to the higher incidence of keloid formation seen in darker skinnedindividuals.