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Ethnic Skin Care

By: Heather Woolery-Lloyd, MD
Posted: October 24, 2006, from the November 2006 issue of Skin Inc. magazine.

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Salicylic acid
     Salicylic acid is common in many OTC acne formulations in concentrations of 0.5–2.0%. Irritation and postinflammatory hyperpigmentation in predisposed consumers usually are observed with higher concentrations. Salicylic acid also can be used as a chemical peel for patients with acne and hyperpigmentation. It is well-tolerated in concentrations of 20–30% in consumers with oily acne-prone skin. Salicylic acid peels do not need to be timed or neutralized, and are applied every two to four weeks for a series of five treatments.

Glycolic acid
     Glycolic acid also is common in many OTC acne and anti-aging formulations. Formulations of up to 10% can be found in anti-aging creams and acne treatments, and up to 20% in some cleansers. It is important to note that the efficacy of glycolic acid is based on the proportion of free acid in a given product. The amount of free acid can be determined from the pH level and the concentration of glycolic acid in a product. Thus, when comparing two products with the same percentage of glycolic acid, the pH is very important. A product with a very low pH will be more irritating but will have a greater amount of free acid and, thus, will be more efficacious at increasing cell turnover and exfoliation. A product with a higher pH will be gentler and have humectant properties but will not be as efficacious in cell renewal.9 
     Glycolic acid also is utilized as a superficial chemical peel. Glycolic acid peels at 20–30% can be used safely on ethnic skin, but they need to be timed and neutralized 2–3 minutes after application. Higher-concentration peels have a greater risk of causing hyperpigmentation in ethnic skin—types IV–VI—because these peels can be significantly deeper. As with salicylic acid, repeated treatments are required in order to achieve the best results.

Hydroquinone
     Hydroquinone is the treatment of choice for hyperpigmentation in the United States. Formulations at 2% are available OTC; 4% formulations are commercially available with a prescription. Often, compounded formulations of 6–10% are required in clients with ethnic skin. Most people with ethnic skin tolerate hydroquinone well. However, there is a small percentage of people with hydroquinone sensitivity who develop irritation and hyperpigmentation with hydroquinone use. In these clients, the degree of irritation increases with the ingredient concentration. 
     Another common issue with hydroquinone is its tendency to oxidize and turn brown when exposed to the air. Hydroquinone packaged in jars frequently turns brown within weeks, once opened. It must be stabilized and packaged in tubes or pumps in order to avoid this problem. 
     Although hydroquinone has been used for more than 40 years in the United States as a skin-lightening agent, OTC formulations of the ingredient are banned in Europe and Asia due to reports that it was carcinogenic in animal studies. 
     Ochronosis is a rare idiopathic darkening of the skin that has been reported with prolonged hydroquinone use. Most cases occurred in South Africa where hydroquinone and other skin-bleaching agents were used daily to lighten facial skin. Hydroquinone has been banned in South Africa due to the high incidence of ochronosis in that country. Interestingly, reports of ochronosis are rare in the United States. Ochronosis most often is associated with prolonged daily application of hydroquinone to the entire face for a period of 20–30 years. For this reason, most dermatologists recommend that the ingredient be applied only to the affected area and that its use be discontinued once improvement has been achieved.

Skin-bleaching agents
     Many other skin-bleaching agents can be used to lighten the skin. These include mequinol, azelaic acid, kojic acid, arbutin, soy, vitamin C, licorice extract and niacinamide. Mequinol is used widely in Europe as a skin lightener. It is the monomethyl ether of hydroquinone, and was introduced recently in the United States as a prescription skin-lightening agent. Azelaic acid 15–20% requires a prescription and has been found comparable to 2% hydroquinone in studies.10 Kojic acid is available OTC in formulations of 4% and also is comparable to 2% hydroquinone.11 Soy and arbutin are available in many OTC products as skin-lightening agents. Although the list of skin-bleaching agents is extensive, hydroquinone remains the gold standard. Significant research in this area is still is needed in order to find equally effective alternatives.

Additional considerations
     Moisturizers are an extremely important component of ethnic skin care. Patients with darker skin types often develop a gray appearance to their skin when it is dry. This phenomenon frequently is referred to as “ashy” skin. In fact, some studies suggest that transepidermal water loss is greater in black patients.12 This finding may account for the high incidence of dry skin seen clinically in black clients. Highly effective moisturizers often are required to treat this ashy appearance. In more severe cases, moisturizers with ingredients such as lactic acid or salicylic acid are most effective. 
     Another common concern for clients with ethnic skin is the gray tint observed with the application of topical sunscreens that contain zinc oxide or titanium dioxide. Similarly, foundations and makeup that contain physical blockers tend to cause this gray/blue tint or hue to the skin. This gray sheen is most prominent in types V and VI skin, and can make certain sunscreens cosmetically unacceptable for ethnic skin. 
     Micronized formulations have made these physical blockers more cosmetically acceptable. Other solutions include combining chemical blockers with physical ones so that a lower concentration of the physical blocker is required in order to achieve the desired SPF. Despite these advances, developing a purely physical blocker with a high percentage of zinc oxide or titanium dioxide that does not leave a gray hue or tint on darker skin types remains a challenge. 
     Additionally, other topical products that leave any type of residue are not cosmetically acceptable in ethnic skin. This is because a thin white residue that is transparent in lighter skin can be extremely obvious in darker skin tones. This phenomenon has been observed in some urea and benzoyl peroxide products. However, it can occur in any topical product that leaves a powdery residue when it dries on the skin.
       
Summary
     The cosmetic concerns of ethnic skin are unique and varied. Skin sensitivity appears to be similar among different racial ethnic groups.13 However, the aftereffects results of skin irritation in darker-skinned persons are more pronounced. Although most products are well-tolerated in ethnic skin, it is important to understand the unique features of this ethnic skin type when recommending treatments.