The skin is composed of two layers, the epidermis (superficial layer) and the dermis (deep layer). Hyperpigmentation, which is characterized by the darkening of skin due to overproduction of the pigment melanin, can occur in both of these layers. Knowing in which layer the excess pigment lies is essential to developing the best and most efficacious treatment plan.
How to distinguish between the two
Distinguishing the difference between epidermal and dermal hyperpigmentation is quite simple. In natural UV light, epidermal pigmentation appears light to medium brown, while dermal pigmentation most often appears dark brown, blue or gray.
Another way to distinguish between the two is through a Wood’s lamp, which is an incredibly useful diagnostic tool found in most dermatologists’ offices. This lamp emits a black light (short wave ultraviolet light) which is invisible to the naked eye, but glows violet in a dark environment. It effectively determines the depth of melanin in the skin by highlighting the color contrast of pigmentation lesions. Epidermal pigmentation will fluoresce under a Wood’s Lamp, showing clear contrast (deeper color) while dermal pigmentation will not fluoresce, showing little to no change in contrast.
Epidermal hyperpigmentation refers to increased melanin deposition in the uppermost layer of the skin. It is typically short lived and easily treated with a regimen that comprises adequate sun protection, chemical exfoliators (alpha hydroxy acids) and melanogenesis suppressing ingredients such as vitamin C, tyrosinase inhibiting plant extracts (licorice extract, rumex extract, bearberry extract), and niacinamide (inhibits melanosome transfer from melanocytes to keratinocytes in the basal layer of the epidermis).
Pigment that has reached the dermal layer is far greater to remove than pigmentation found in the epidermis. Topical skin lightening products are of little use as they cannot penetrate the dermis. Treatment of dermal hyperpigmentation instead requires the use of lasers and/or medium-depth chemical peels.
Medium-depth chemical peels involve the use of chemical agents (trichloracetic acid, Jessner’s solution, glycolic acid, or solid carbon dioxide) to wound the skin in a controlled manner, triggering regenerative processes that subsequently result in the healing and treatment of various skin disorders in the epidermis and papillary dermis. The gold standard for medium-depth peels have become a combination of the chemical agents listed above. Examples include:
– 70% glycolic acid + 35% trichloracetic acid
– Jessner’s solution + 35% trichloracetic acid
– Solid carbon dioxide freezing + 35% trichloracetic acid
Like with most skin peeling treatments, medium-depth chemical peels require a series of treatments to remove dermal pigmentation as well as downtime.
Mixed (dermal and epidermal hyperpigmentation)
Hyperpigmentation that occurs in both the epidermis and dermis requires a multifaceted combination approach that consists of topical skin lightening products and lasers or medium-depth chemical peels.
Determining the location of melanin deposition in the skin can be achieved by the naked eye or the Wood’s lamp and helps to provide a clear diagnosis and the correct treatment plan.