j. Cosmet. Sci., 51, 153-167 (May/June 2000) Development of a modified forearm controlled application test method for evaluating the skin mildness of disposable wipe products MIRANDA A. FARAGE, Baby Care Products, The Procter & Gamble Company, 11450 Grooms Road, Cincinnati, OH 45242. Accepted for publication March 15, 2000. Synopsis A modified forearm controlled application technique (modified FCAT) was developed to evaluate the relative mildness of baby wipe products. The test uses a semi-occlusive patch system to mimic the hydrated conditions common to the skin in the diaper area, interspersed with repeated product applications. The skin condition is scored for four endpoints: visual scoring for erythema and dryness, and instrumental scoring for redness (using a chromameter) and transepidermal water loss (TEWL by evaporimeter). The variables evaluated in the course of developing the method include the optimum patch system to achieve hydration, the specific procedure for applying the test products, and the minimum test duration required to achieve significant differences for all four endpoints. The optimum study design produces statistically significant differences between baby wipe test products in all four endpoints. This method has applicability for wipes intended for other uses where mildness and irritation are critical considerations, such as wipes intended for cosmetic removal. INTRODUCTION An important part of the safety assessment for new consumer products is an evaluation of potential skin effects. Initial evaluations may include patch tests on ingredients or on complete formulations for the potential to cause skin irritation or contact sensitization. For some consumer products, no additional testing is required. However, for products where expected use involves prolonged or repeated contact with the skin, additional testing is necessary to evaluate more subtle skin effects that may contribute to consumer acceptance of the product. Several tests have been developed over the years to evaluate household and personal cleansing products for potential irritant effects under conditions that mimic product use. Examples include the hand immersion test (1), the repeated open application test (2), the flex wash test (3), and the forearm controlled application technique (FCAT) (4). We were interested in evaluating the skin effects of a very specialized consumer product, baby wipes. The intended use of baby wipes offers a unique challenge. The skin under- neath a baby's diaper is almost always in a state of hydration as a result of the presence 153

154 JOURNAL OF COSMETIC SCIENCE of moisture and the semi-occluded nature of a diaper. Transepidermal water loss (TEWL) readings for baby's skin in the diaper area are markedly higher than TEWL readings for undiapered skin. As a result, diapered skin demonstrates a background level of irritation that can mask slight differences in the effects produced by different products. Clinical studies, where a panel of consumers actually use the products under evaluation for an extended period of time, have been used to study mildness and other skin effects. However, such studies for baby wipe products are extremely costly and time-consuming. Further, there are a number of factors that can confound the results, such as the ap- pearance of diaper rash, heat rash, yeast infections, bacterial infections and other skin diseases, or variations in the use habits and practices of parents. A practical, cost-effective test method was needed that would evaluate the relative mildness of various product formulations on skin that was in a state of hydration. Other investigators have been successful using the FCAT to determine the relative mildness of a variety of personal cleansing products (5). Therefore, we chose to develop a modified FCAT specifically for evaluating baby wipes. The developmental program consisted of two phases run concurrently. The patch system development phase involved four small-scale tests designed to devise a practical and effective system for producing hydrated skin in the test site area. The two main variables examined were: (a) the use of synthetic urine versus water for hydration, and (b) the patch system used to achieve a semi-occluded environment. The FCAT modification phase involved three tests using baby wipe products. The main variables examined in this phase were: (a) the specific duration of test product application, (b) the need for a conditioning or pretreatment period, and (c) the minimum overall test duration and number of subjects required to achieve significant differences between products. MATERIALS AND METHODS PATCH DEVELOPMENT PHASE Materials. Modified diaper patches were 4" x 6" rectangles cut from the core area of commercially available disposable diapers (Pampers Baby Dry©). These were saturated with 60 ml of fluid and applied to test sites by wrapping the diaper patch with Kerlix © mesh and securing it with 3M Blenderin © tape. Alternatively, patches consisted of Johnson 8: Johnson Band-Aid © Brand large adhesive pads (27/8" x 4") saturated with 5 ml of fluid. In some experiments, the adsorbent pad of the bandage was supplemented with a 3" x 3" sterile gauze pad folded once, and/or the bandage adhesive was reinforced with Blenderin © tape. When the gauze pad was used together with the bandage, 9-10 ml of fluid was used to saturate the patch. Synthetic urine consisted of 0.2% KCI, 0.2% Na2804, 0.085% (NH4)H2PO4, 0.05% MgCI 2 ß 6H20, 0.025% CaCI 2 2H20 , and 0.015% (NH4)2HPO4 in deionized water. FCAT MODIFICATION PHASE Materials. Four different currently marketed baby wipes were used in these experiments. These are referred to as products A, B, C, and D. All four of these products have been safely marketed for many years. Products A and B were Procter & Gamble brands. Internal, unpublished data available on these products indicate they are "very mild" in