A comprehensive review examined the primary causes and potential solutions for body skin pigmentation.

In the study, published in the Journal of Dermatologic Science and Cosmetic Technology, investigators provided an in-depth analysis of melanin formation mechanisms, influential factors, and various approaches to skin whitening.

The investigators conducted an extensive literature review, synthesizing information from various studies on skin pigmentation mechanisms, factors influencing pigmentation, and whitening strategies. They analyzed data from previous research on melanin synthesis pathways, signaling cascades, and the effects of various internal and external factors on skin pigmentation.

The review incorporated findings from in vitro studies, clinical observations, and molecular analyses to provide a comprehensive understanding of body skin pigmentation processes and potential interventions.

Among the key findings were:

• Melanin synthesis, transport, and degradation were identified as the primary processes governing body skin pigmentation.
• External factors like ultraviolet (UV) radiation and internal factors such as gender, age, weight, and hormones significantly influenced skin pigmentation.
• Body skin exhibited slower keratin metabolism compared with facial skin, leading to a higher likelihood of dullness.
• Effective body skin whitening strategies included sun protection, interference with melanin formation, promotion of stratum corneum metabolism, and prevention of inflammation.

The study outlined four major stages in the process of melanin deposition:

• Premelanogenic signaling
• Melanogenic stage
• Melanin transport
• Melanin metabolism.

The investigators identified several key signaling pathways involved in melanogenesis, including:

• MC1R/α-MSH signaling pathway
• PI3K/Akt signaling pathway
• MAPK signaling pathway
• NO signaling pathway.

The melanin synthesis process involved the conversion of tyrosine to dopaquinone (DQ) under tyrosinase catalysis, followed by a series of reactions leading to the formation of eumelanin and pheomelanin.

External factors affecting body skin pigmentation:

• UV radiation was identified as the major contributor to increased or redistributed pigmentation in the epidermis. The study reported that prolonged exposure to light resulted in a twofold increase in melanocyte count compared with light-protected skin.

Internal factors affecting body skin pigmentation:

• Gender: Adult males exhibited lower L* values (darker skin tones) and higher a* values (redder skin tones) compared to adult females.
• Age: L* values decreased for the forehead, cheek, flexor side of the forearm, and dorsum of the hand as individuals aged, indicating darkening of skin tone.
• Weight: A significantly higher detection rate of pigmentation was observed in both overweight and obese groups compared with the regular weight group (P < .01).
• Sex Hormones: Estrogen receptors were found to be more abundantly expressed in melasma lesions compared with normal epidermis.

The review provided several specific data points:

• 65% of melanocytes responded to estrogen stimulation by enhancing their activity and increasing melanin secretion levels.
• In an in vitro model of skin, complete inhibition of UVR-induced tanning was observed by blocking PAR-2 activation with a soybean trypsin inhibitor.
• The detection rate of pigmentation increased significantly with an increasing degree of overweight (P < .01).
• Body mass index (BMI) was significantly higher in the hyperpigmentation group for both sexes (P < .01).

The review presented several approaches to body skin whitening:

• Sun Protection: The importance of using sunscreen products with appropriate SPF and PA ratings was emphasized, particularly for body skin which was more susceptible to tanning.
• Interference with Melanin Formation: Inhibition of tyrosinase activity, inhibition of dopachrome isomerase activity, and inhibition of oxidation reactions.
• Inhibition of Melanin Transport: Niacinamide and tannic acid were identified as effective ingredients for inhibiting melanosome transfer.
• Accelerated Melanin Degradation: The study highlighted the role of autophagy in keratinocytes for melanin degradation, with ginsenosides shown to regulate this process through the AKT/GSK3β/β-catenin signaling pathway.
• Stratum Corneum Metabolism: Physical and chemical exfoliation methods were discussed as means to promote epidermal cell detachment and improve skin tone.
• Prevention of Inflammation: The study emphasized the importance of incorporating anti-inflammatory compounds in cosmetics to delay inflammation-induced hyperpigmentation. Pine pollen extract, bamboo leaf extract, and bisabolol were shown to inhibit cytokine interleukin (IL)-1β production.

Authors are currently employed by Shandong Huawutang Biotechnology Co., Ltd.