j. Soc. Cosmet. Chem., 39, 355-366 (November/December 1988) Forearm wash test to evaluate the clinical mildness of cleansing products MICHAEL F. LUKACOVIC, FRANK E. DUNLAP, SCOTT E. MICHAELS, MARTHA O. VISSCHER, and DEBRA D. WATSON, The Procter and Gamble Company, Sharon Woods Technical Center, Cincinnati, Ohio (M.F.L., S.E.M., M.O.V., D.D.W.), and Cosmetic Research, Inc., Tucson, Arizona (F. E.D. ) Received November 9, 1987. Synopsis A forearm wash test was developed to differentiate the mildness of personal cleansing products, e.g., bar soaps. The wash protocol was derived from habit information and by observation of actual wash situations. The method was found to be sensitive enough to discriminate differences in bar composition such as tallow/coconut ratio, presence of super fitting, and type of synthetic surfactant. There are design variations to accommodate paired comparisons and single product comparisons of multiple products. Dew point was a key indicator of responsiveness to soap treatment. Therefore, the number of washings was increased to allow product differentiation under conditions of high dew point. Because the method was derived from actual washing situations, it is more likely to be predictive of consumers' skin condition when using cleansing products than are the conventional chamber or patch tests. INTRODUCTION The soap chamber test developed by P. J. Frosch and A.M. Kligman (1) has been used to evaluate soaps for their effect on skin attributes such as erythema, scaling, and fis- suring. At the 43rd annual meeting of the American Academy of Dermatology, Kligman et al. described an exaggerated-use face wash test to evaluate several skin- cleansing products. In a later study that evaluated several skin-cleansing products using an exaggerated-use face wash test, Kligman (2) concluded that washing tests are more relevant and reliable than the chamber test. Sauermann et al. (3) concluded that the application of soap solutions under chamber test conditions caused inflammation that was not relevant to normal regular use. Other studies (4-6) indicate that skin condition is affected by humidity, temperature, and cleanser or bar formulation, e.g., surfactant type. In this paper we describe a forearm wash test and present clinical results obtained with it. Mildness is defined by the parameters of skin redness, dryness, and smoothness. The results include evaluations by expert graders (dermatologists or graders trained and 355

356 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS supervised by dermatologists), with confirmatory data from transepidermal water loss (TEWL) measurements. Conclusions are as follows: (1) The method can differentiate bar soaps for skin mildness. (2) Skin condition can be related to several bar soap formulation variables. (3) Factors that can affect test results, such as climatic conditions, sex, and initial skin condition, can be controlled by the test design. (4) The test design can be either a paired-comparison or single product design. (5) TEWL measurements corroborate the expert visual assessment of redness and dry- ness. MATERIALS AND METHODS SUBJECTS: ELIGIBILITY AND NUMBER Informed consent was obtained from adults, 18-55 years of age, who regularly washed with soap. Excluded was any subject who (1) had an initial dryness grade of 3.0 or higher (0 = no dryness, 3 = moderate dryness, on a 0-6 scale described in Table I) on either forearm as assessed during the initial examination, (2) had skin cancer, eczema, or psoriasis on the forearms, (3) was receiving injectable insulin, (4) was pregnant or lactating, or (5) was receiving treatment for skin problems or contact allergy. In the early stages of the method development, base sizes of about one hundred subjects per treatment group were used. However, groups of 25-30 subjects were later found to be adequate for discriminating product differences. RESTRICTIONS Subjects were instructed to avoid hot tubs, swimming, and sun lamps, and to refrain from applying any soaps, cleansing products, creams, lotions, or gels to their forearms for the duration of the study. Further, subjects were instructed to keep water off their forearms for at least two hours before grading. PAIR TEST DESIGN The method of paired comparisons is applicable in this situation, when competing test products can be assigned to contralateral forearms so that subject-to-subject variability is eliminated. The assignment of test products was balanced by initial skin dryness grade, skin color, sex, age (in large studies), and pair order. For example, if the test products were coded P and H, equal numbers of subjects were assigned to use P on the left forearm, H on the right forearm, and vice versa. The studies were conducted in a double-blind manner. SINGLE PRODUCT TEST DESIGN Although this design results in greater variability and, therefore, provides less statis- tical control than the pair test, it offers greater flexibility and economy in testing many products or formulations when all inter-product comparisons are equally important. In this design, both forearms were washed with the same test product, and the subjects