Human skin is characterized by significant diversity in color and tone, which are determined by the quantity and distribution of melanin pigment in the epidermis. Increased content of melanin in combination with the extrinsic stress factors causing inflammation such as excess UVR, allergic reactions, or injury can also frequently lead to cosmetic problems resulting in discoloration and scarring and molecular signatures of one of the most common problems, post-inflammatory hyperpigmentation (PIH).
Post-inflammatory hyperpigmentation (PIH) is characterized by an uneven distribution of melanin and dark spots, which can range in color depending on the severity of the damage and skin tone. Acne and atopic dermatitis, allergies, traumas, and cosmetic operations can all cause PIH triggered by the synthesis and release of extra melanin by melanocytes in the epidermis. Endogenous factors, including hormonal changes or systemic diseases, can also contribute to the more prevalent occurrence of PIH. Current treatments of PIH involve products that lighten the pigment, prevent its accumulation or stimulate cell renewal. Cosmetic treatments for discoloration reduction are frequently based on chemical peelings, other treatments include laser technology, which is used not only to lighten the discoloration but also to reduce the appearance of some scars. However, such procedures can lead to complications involving dermal melanin deposition and exasperating inflammation, particularly in dark skin.
ORIGIN
origin of PIH points to inflammation, which contributes to the damage of the basal layer of the epidermis and acts as a trigger for melanocytes to release melanosomes containing pigment to the surrounding skin cells; the pigment granules can persist for a prolonged time leading to further discoloration of the epidermis. Damage to the basement membrane and basal keratinocytes, which release melanin in large quantities in response to inflammation, can also lead to PIH in the dermis. In the upper dermis, the pigment is phagocytosed by macrophages, giving the skin a darkened appearance; this type of hyperpigmentation can be either prolonged or permanent.
The proposed systemic mechanisms of hyperpigmentation in dark skin are outlined in Figure. The model predicts that the susceptibility to low-grade chronic inflammation combined with the structural organization and increased secretory activity of upper skin layers would constitute a partial mechanism driving the hyperpigmentation in darkly.
Prevention and treatment of PIH can be achieved with photoprotection using broad-spectrum sunscreens as well as natural ingredients inhibiting the melanogenic pathways and causing depigmentation whilst reducing inflammation. Current trends support the discovery of novel formulations to address both cosmetic and biomedical aspects of PIH
Reference: Post-Inflammatory Hyperpigmentation in Dark Skin: Molecular Mechanism and Skincare Implications https://doi.org/10.2147/CCID.S385162
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