198 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS All daily shed hair collections during the two-week baseline and four-week treatment phases were placed in premarked envelopes and sealed daily. The subjects recorded whether they shampooed their hair or not. To ensure compliance in hair collections, field workers visited each subject's home very two to three days throughout the study to collect the envelopes of hair and distribute new envelopes for the next set of hair collections. All envelopes of hair were taken to the Thai Institute of Dermatology for evaluation. A team of eleven nurses, supervised by four dermatologists, counted and typed all the hair collected from the study. Each day's hair collections were counted, examined, and categorized as telogen, anagen, and broken hairs. During the study, it was noted that some of the hair collections contained small pieces of hair resulting from haircuts. The cut hair was recorded separately from the broken hair and not included in the analyses of total hair loss count. At the termination of the treatment period, the subjects underwent a final scalp and hair examination. In addition to the hair and scalp evaluations at the baseline and posttreatment periods, subjects were requested to complete self-assessment questionnaires designed to obtain information regarding their perception of hair fall and hair health. The perceptual questions pertaining to hair fall and hair health were based on a 0-to-7-point scale where 0 represented the absence of a particular hair condition, 4 represented that they per- ceived a moderate condition, and 7 represented that they perceived a severe condition. Subjects were requested to describe the state of their hair health, amount of damage, manageability, thickness, coarseness, fluffiness/fly away, weight of hair, and dryness/ oiliness. In addition, they were requested to assess the state of their scalp health, dandruff severity, hair fall severity, scalp itch, scalp dryness, and scalp irritation. In an attempt to understand why consumers associate hair fall with the use of shampoos, a series of questions was posed to the subjects in this study to determine their perception of the possible causes of hair fall, hair thinning, and hair loss tendencies. DATA ANALYSES Wilcoxon rank sum tests were performed on the mean total, telogen, anagen, and broken hair loss rates at the baseline and treatment periods, and on the differences in total, telogen, anagen, and broken hair loss rates from the baseline to the treatment periods on a daily basis and on shampoo and non-shampoo days. In addition, regression analyses were performed on the differences in the mean total, telogen, anagen, and broken hair loss rates on shampoo versus non-shampoo days. The subjects' perceptions of hair and scalp health were assessed using Wilcoxon rank sum tests on the differences in ratings given by the subjects on the hair and scalp attributes during the baseline and treatment periods. Wilcoxon rank sum tests were performed on the mean number of uses of test product and product consumption. Comparisons with p values of •0.05 were considered statistically significant. Frequency analyses were performed on the subjects' perceptions of possible causes of hair fall, hair thinning, and hair loss tendencies. RESULTS Of the 460 subjects screened for potential participation in the study, 440 subjects were

ABSENCE OF EFFECTS OF DIMETHICONE ON HAIR LOSS 199 accepted to participate and 404 subjects completed the study. Of the 36 subjects who did not complete the study, 29 subjects (6.6%) discontinued participation in the study prior to termination on their own initiative. The hair loss data from another six subjects (1.4%) were eliminated because of missing hair collections at the baseline and/or the treatment phases of the study. In this study, three subjects reported that they experienced adverse reactions during the product use phase of the study. These subjects were examined by the investigators, and their reactions were deemed to be unassociated with treatment. One subject claimed that she had hair loss. She was examined and no evidence of abnormal shedding was found. This subject continued to participate in the study uneventfully until termination. However, the hair loss information was not included in the data analyses because the subject switched from using the treatment shampoo to her own shampoo temporarily after she thought she experienced hair loss. A second subject discontinued participation after reporting that she developed a rash while using the product. Examination showed her scalp to be normal, and no rash was present. A third subject discontinued partic- ipation after reporting that she had an itchy and sore scalp. She was found to have dandruff. Each of the three subjects was on a different shampoo treatment. Statistical analyses conducted on the mean total, telogen, anagen, and broken daily hair loss rates at baseline and treatment, and differences in the total, telogen, anagen, and broken daily hair loss rates from baseline to treatment periods indicate no significant differences in the mean daily hair loss rates between the three shampoos tested in this study (Table I). The mean total hairs lost ranged from 28 to 35 hairs per day. These daily hair loss rates are consistent with reported findings in the normal population (2-3,8). No significant differences were noted in the mean daily hair loss rates during the baseline and treatment periods between the three treatment groups (Figures 1, 2, 3, 4). Statistical analyses conducted on the mean total, telogen, anagen, and broken daily hair loss rates on shampoo versus non-shampoo days indicate no significant differences in the hair loss rates between the three shampoos (Table II). However, as expected, signifi- cantly more total, telogen, and broken hairs were lost during the shampoo days as a result of the hair grooming process (Table II). Assessment of abnormal hair loss pre- to posttreatment using the pull test (3) indicate that there was no abnormal hair loss at pretreatment. Overall, less than one hair was obtained per subject in each trial of the pull test (3). There were no differences between the number of hairs lost from the pull test during the baseline or posttreatment exam- ination periods. Evaluations of the short hairs at the hair parts confirmed that subjects had tapered rather than blunt distal hair tips pre- and posttreatment, indicating normal hair regrowth rather than broken hairs. No abnormal hair loss was evident in these subjects at baseline and posttreatment. The subjects' medical and dermatologic history profiles were unre- markable. Scalp examinations performed during the baseline and posttreatment periods showed no significant differences in scalp flaking. No scalp erythema was observed in the pre- or posttreatment examinations.