Pigmentary changes skin preparation

As a general rule, it is worthwhile preparing the skin carefully with tyrosinase inhibitors if there is any risk of post-peel pigmentary changes or to optimize results when treating melasma. Retinoic acid and sometimes glycolic acid are used to make transepidermal penetration more even or to deepen the action of the acid solution. 

Before any classic peel, steps must be taken to limit the risk of pigmentary changes. Preparing the skin with tyrosinase inhibitors (hydroquinone, kojic acid, azelaic acid, arbutin, Morus Alba, licorice extracts, etc.) is especially recommended to curb the enthusiasm that certain melanocytes have for converting tyrosine into melanin. Preventive measures should begin 3-4 weeks before a medium or deep peel. 

TCA-SAS should be preceded by several weeks of skin preparation to even out and reduce the thickness of the stratum corneum, reduce melanocyte activity and enhance re-epithelialization. ETCA, on the other hand, is applied on unprepared skin, as the acid and the post-peel cream penetrate evenly the risk of pigmentary changes (basic protocol) is extremely low and re-epithelialization takes place without prestimulation. 

Unfortunately, there is another significant problem with water-based AHAs they do not penetrate evenly. They penetrate more quickly in areas where the stratum corneum is thinner - and therefore more permeable - and more slowly where the stratum corneum is thicker. They penetrate more slowly on the oilier parts of the face and more quickly where the skin is dry, infected or irritated. It is therefore essential to prepare the skin for 2-3 weeks before the first water-based AHA peel to even out the thickness of the stratum corneum. The melanocytes also need to be stabilized to avoid any potential pigmentary changes. 

If the melanin responsible for the melasma is too deep, TCA will only be effective after many repeated sessions. In any event, the TCA peel must be combined with effective sun protection and appropriate post-peel care in the long term. Simple aqueous solutions of TCA also require the skin to be prepared, in order to even out penetration and prevent common pigmentary changes. 

Not counting the importance of skin preparation, the adjuvants used, technical errors and preventive postpeel care and treatment, the risk of pigmentary changes can be quantified diagrammatically as follows ... 

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