Prior to chemical peel application, there are important risk factors to consider. Understanding these risk factors will help to reduce side effects and will help to achieve optimal clinical outcomes. Risk factors are especially crucial to consider with layered peel application and caution should be taken with certain ethnic groups. When treating ethnic skin, it is essential to have a thorough understanding of skin histology, darker toned ethnic groups, and the side effects of inflammation ultimately leading to melanogenesis and post-inflammatory hyperpigmentation.

INFLAMMATION
There are two types of inflammation that can occur after a peel procedure. Acute inflammation is common and is short in duration. If left untreated, acute inflammation can continue and progress to chronic inflammation. Chronic inflammation can last for days and is commonly found with layered peels or medium depth chemical exfoliation. Chronic inflammation should be addressed with topicals that can resolve the inflamed tissue and assist the skin during the repair process to avoid permanent pigment scarring.

The inflammatory process is involved with cosmetic procedures, such as chemical exfoliation, and is the skin’s natural defense to repair itself. The inflammatory process occurs as a response of the body’s innate immune system, where white blood cells are alerted to respond and defend against small inflammatory processes. It is during the inflammatory process where fibroblasts are stimulated to rebuild new collagen. The inflammatory process that a number of inflammatory mediators, including prostanoids, cytokines, chemokines, as well as reactive oxygen species. In the dermis, inflammation can disrupt the basal layer of the epidermis causing melanocytes to become trapped in the macrophages of the papillary dermis. As a response to the chemical peel, the inflammatory response can alter the activity of melanocytes and immune cells in both the epidermis and dermis, thereby increasing production of melanin, ultimately leading to melanogenesis and post-inflammatory hyperpigmentation.

MELANOGENESIS
Melanogenesis is the process in which skin cells produce melanin. It begins within melanocytes, which are the cells that create pigment found in the skin, eyes, and hair. Melanocytes produce melanosomes and comprise approximately 10 percent of the cells in the basal layer of the epidermis. Synthesis of melanin occurs exclusively in melanosomes from melanocyte activity. The difference between fair skin and dark skin is not due to the quantity of melanocytes, but is due to the size and the level of activity of melanocytes. Darker racial ethnicities are at a higher risk of melanogenesis due to an increase in melanocyte activity during the inflammatory stage.

TYROSINASE
Tyrosinase is an enzyme that is produced during melanogenesis, from the amino acid tyrosine, and is required for melanocytes to produce melanin. Studies have found that a protein complex formed by the enzyme tyrosinase and dopachrome tautomerase is mainly found in dark skin melanocytes which induces sustained tyrosinase activity. The sustained tyrosinase activity can result in hyperpigmented conditions commonly found with skin phototypes III to VI. With chemical exfoliation, agents that interfere or block the production of tyrosinase should be considered essential therapy prior to chemical exfoliation to help inhibit melanogenesis during the inflammatory stage. This is especially important for those of darker racial ethnicities or for those who are prone to post- inflammatory hyperpigmentation.

OPTIMAL PROTOCOL
With chemical exfoliation and medium depth peels, keratinocytes within the epidermis are responsible for restoring the epidermis through a process called epithelialization, which is an essential component of the repair process. Chronic inflammation that may occur postoperative chemical exfoliation may impair the process of epithelialization and re-epilation of skin cells. Re-epilation of skin cells involves the migration and proliferation of keratinocytes, which depends on the interaction of keratinocytes with dermal fibroblasts and the extracellular matrix.

Assisting the skin through the repair process with tissue-regenerating topicals will help to reduce risk factors and offer optimal clinical outcomes. Clinical-based ingredients, such as GHK-Cu copper peptides, atelocollagen, human growth factors, and processed skin cell proteins, will assist the skin during the re-epilation stage and are ideal postoperative therapy after a chemical peel procedure. With any type of chemical peel, conditioning the skin weeks prior to the procedure with alpha hydroxy acids or retinols will help to reduce risk factors with dark skin phototypes. Enzyme peels or alpha hydroxy acids composed of a large form molecule, such as lactic acid or mandelic acid, will provide optimal results for dark skin phototypes with little irritation. Hydroxy acids, such as polyhydroxy acids, are ideal for sensitive skin and dark skin phototypes and will help to improve the skin barrier. Tyrosine inhibitory topicals such as kojic acid, arbutin, mandelic acid, or retinols will help to inhibit tyrosinase and increased melanogenesis stimulated as a result of inflammation.

Linda Gulla is a NSPEP physician-endorsed master aesthetician and is a published writer in cosmetic dermatology whose material has been reviewed and endorsed by dermatologist Dr. Eric Schweiger, as well as the renowned Dr. Abdala Kalil. As a published writer, Gulla’s expertise can be found in the “Milady Advanced Esthetics” 2nd Edition. Gulla has shared her expertise with family physicians and dermatologists as an adjunct instructor with the National Procedures Institute, where her material was reviewed by over seven medical review boards and was ACCME accredited. Gulla is founder of the Institute of Advanced Aesthetics and Health Sciences and is recognized as an approved provider with the NCEA COA. Her online self-study program can be found at iaahs.com. Professionals can obtain additional reference material that covers this entire series on Chemical Resurfacing in Dermatology and Advanced Layered Peels by visiting her website at iaahs.com.