244 JOURNAL OF COSMETIC SCIENCE skin cells (16-25). There is also some evidence that products containing AHAs may deliver longer term benefits such as reduced lines and wrinkles and improved skin firmness, smoothness, and elasticity (26-29). The number of reported adverse reactions to skin care products containing AHAs prompted the Food and Drug Administration (FDA) to question the safety of these products. Typical complaints received by the FDA from consumers using AHA- containing products have included facial redness, swelling (especially in the eye area), burning, blistering, bleeding, scarring, rash formation, itching, contact dermatitis, and skin discoloration. The Cosmetic Ingredient Review (CIR) completed a review of the safety of two of the most commonly used AHAs in cosmetics, glycolic acid and lactic acid, as well as their salts and esters. The CIR concluded that AHAs are generally safe as used in most cosmetic preparations, but recommended that total AHAs not exceed 10% in commer- cial cosmetics with a final pH greater than or equal to 3.5, and not exceed 30% in salon products for use by trained professionals with a final pH greater or equal to 3.0. The CIR also recommended that cosmetic and salon products be formulated to avoid increased sun sensitivity or contain directions for use that include the use of daily sun protection (30-32). As originally noted by Yu and Van Scott (33), the bioavailability of AHAs in cosmetic products depends on the pH of the preparation as well as the concentration of AHAs. A preparation containing 10% glycolic acid at a pH of 3.0 will generally be over twice as active on the stratum comeurn as a preparation containing the same amount of glycolic acid at a pH of 4.0. Because of continued uncertainty about the long-term effect of AHA use on the skin and the skin's vulnerability to UV radiation, the FDA has begun a long-term study to identify the concentration of AHAs in cosmetic and salon formulations on the market and the pH of those formulations. The present study reports the FDA's latest survey of consumer and salon products containing AHAs and draws upon the analytical methods developed at the FDA (34) and at other research centers, using ion pair reverse-phase high-performance liquid chromatograpty to analytically and quantitatively separate gly- colic acid, lactic acid, and other AHAs from cosmetic products (35,36). To improve separation, this work also relied upon pre-column purification methods employing solid- phase extraction (34). This, data along with that collected previously, will be used by the FDA to monitor industry conformity with the limits recommended by the CIR. METHOD The extraction and analytical method previously developed by the FDA was used in this study (34). A portion of each cosmetic or salon product was mixed with Celite and packed on top of a C18 solid-phase extraction column. The column was eluted with 0.1 M ammonium phosphate, and analyzed by HPLC using a C8 column, a 0.1 M ammo- nium phosphate mobile phase, and a UV detector set at 210 nanometers. Glycolic and lactic acid peaks were identified by comparison of retention times with known reference standards and were quantified using a standard calibration curve. Finally, the pH of each sample was determined both undiluted and as a 1-to-9 dilution in distilled water.

ALPHA HYDROXY ACIDS 245 RESULTS AND DISCUSSION During this investigation, a total of twenty-five different consumer cosmetic products obtained at stores in the Washington, DC area in 1999 were analyzed for glycolic acid and lactic acid and tested for pH (Table I). About half of the products contained glycolic acid, ranging in concentration from 2% to almost 9%, with an average concentration of 5.6%. Another half of the products contained between 1% and almost 9% lactic acid, with an average concentration of 3.7%. The pHs for both neat and diluted (1/9) products ranged from 3.2 to 9.0, with no significant difference between neat and diluted data. Most had a neat and diluted pH near 4.3. Five of the consumer cosmetic products contained a sunscreen while eight of the consumer cosmetic products contained a rec- ommendation for the use of a sunscreen on the product label. The levels of AHAs in all consumer cosmetic products tested fell below the 10% threshold recommended by the CIR. Twenty-three out of twenty-five products tested also had pHs very near or above the CIR's recommendation for minimum pH. In addition to consumer cosmetic products, seventeen professional/salon products col- lected by FDA inspectors throughout the U.S. in 2000 were analyzed for glycolic acid and lactic acid (Table II). These products were intended for professional use only. Most of these products contained glycolic acid, with concentrations ranging from 0.9% to 28.5%, with an average concentration of 10.5%. Five products contained lactic acid at an average concentration of 4.0%. The levels of AHAs in all salon products fell below the 30% threshold recommended by the CIR however, two products had pHs signifi- cantly below the recommended minimum. None of these salon products contained a sunscreen and only two of them contained a recommendation for the use of a sunscreen on the product label. The absence of chromatographic interference was evidenced by a consistent retention time and peak area for each arialyre in each analysis. R-squared values for calibration curves were typically 0.999 or better. In cosmetic product matrices, recovery of added glycolic and lactic acids ranged from 94% to 105%, with an average recovery of 99% (Table III). In the salon product matrices, recovery of added AHAs ranged from 94% to 106%, with an average recovery of 101% (Table IV). CONCLUSION All of the consumer cosmetic products and salon style products tested in this study met the CIR's recommendations for AHA concentration. Two out of a total of twenty-five consumer cosmetic products had pH values below that recommended by the CIR. Two out of a total of seventeen salon products had pH values below that recommended by the Table I Concentration of Glycolic and Lactic Acids, and pH, in Consumer Cosmetic Products Alpha hydroxy Concentration Concentration Occurrence acid avg. (%) range (%) frequency Average pH • pH • range Glycolic acid Lactic acid 5.6 1.9-8.7 13 of 25 3.9 3.3-5.6 3.7 1.1-8.7 13 of 25 4.7 3.2-9.0 Neat.