JOURNAL OF COSMETIC SCIENCE 162 MATERIALS AND METHODS FORMULATIONS AND STABILITY EVALUATION Base hair tonic containing PEG 40-hydrogenated castor oil, menthol, ethyl alcohol, bu- tylene glycol, glycerine (Namsiang, Bangkok, Thailand), and water was formulated as shown in Table I. The pH values of the formulated hair tonics were determined using a PC Testr 35 (Oakton Instruments, Vernon Hills, IL) multifunction analyzer. Three base formulas were tested and found to be stable after an accelerated stability test that was based on a centrifugation assay (3000 rpm for 30 min) in a Micromax RF centrifuge (Thermo Fisher Scientifi c, Waltham, MA) and six cycles of heating (45°C) and cooling (4°C) for 48 h for each cycle (11). The hair tonic base was incorporated with green tea extract with 100 mg% of polyphenols (product code: HE-EL11-CAS) supplied by Specialty Natural Products (Chonburi, Thailand). The obtained green tea hair tonics were stability tested as above. PREFERENCE TESTS Preference tests for the base hair tonics were carried out with seven female and three male Thai volunteers aged 23–39 years by using a questionnaire with a hedonic scoring system (scores 1–5, where 1 = dislike, 2 = strong preference). The preferred base, which also passed the stability test, was chosen for further hair tonic development (11). CLINICAL EVALUATION Inclusion criteria. Healthy Thai volunteers aged between 23 and 39 years were enrolled in the study. All recruited subjects were informed about the study both in writing and ver- bally, and signed a written consent form that was approved by the ethical committee of the Mae Fah Luang University before enrollment (REH-58062). All of the studies involv- ing human volunteers were in accordance with the Declaration of Helsinki. Table I Formulation, Stability, and Preference of Hair Tonic Base Ingredient Hair tonic base (%, w/w) A B C D E PEG 40-hydrogenated castor oil Menthol Glycerine 4 — 2 4.5 7 Butylene glycol — 4 2 4.5 7 Ethyl alcohol Deionized water Centrifuge Homogeneous Freshly pH 4.10 ± 0.00 4.00 ± 0.00 4.47 ± 0.06 4.40 ± 0.10 4.37 ± 0.12 Heat cool pH 4.47 ± 0.06 4.33 ± 0.06 4.57 ± 0.15 4.47 ± 0.06 4.47 ± 0.06 Overall preference (%) 77.20 ± 6.41 79.60 ± 4.17 84.40 ± 4.79 80.00 ± 5.40 82.20 ± 4.60 91.7 86.7 81.7

GREEN TEA HAIR TONIC FOR GREASY SCALP 163 Irritation test. A closed-patch test was performed in the same group of volunteer that par- ticipated in the preference test. Base hair tonic was tested with different green tea con- centrations. Water was used as a negative control, whereas 3% sodium lauryl sulfate (Namsiang) was the positive control. Observation was made immediately after removal of the Finn chamber® (8 mm, SmartPractice, Phoenix, AZ), and at 24, 48, and 72 h after removal. The mean irritation index (MII) was calculated (12). Effi cacy evaluation. Twenty healthy Thai volunteers (10 female and 10 male) aged between 23 and 35 years were included. All subjects were allergy free for 1 week, and had not used steroids or topical products for oily or greasy scalp treatment for 4 weeks prior to study enrollment. Subjects who were pregnant, lactating, or dieting were excluded from the study, as were those who reported smoking or drinking of liquor. The subjects were ad- vised not to apply any product onto the scalp the night before starting the study. All subjects were tested for scalp greasiness at baseline using a Sebumeter®. The measure- ment was performed in triplicate at different positions on the same side of the head. The subjects were acclimatized in a waiting room (20 ± 1°C and 40–60% relative humidity) for 30 min before scalp measurements were carried out under the same conditions. A randomized single-blind placebo-controlled study was designed and the volunteers were requested to apply hair tonic once in the morning by a split-head procedure for intrain- dividual comparative trails. The volunteers were directed to use fi ve drops of the green tea hair tonic on one side of the head and the same quantity of base tonic on the other side. The control cleansing shampoo (No More Tears Johnson & Johnson, Bangkok, Thailand) was provided and used for hair washing (10 g/wash) at 2-day intervals (11). Subjects who showed less than 90% compliance with the assigned product were excluded from the study. Effi cacy evaluation was conducted on days 7, 14, 21, and 28 using the Sebumeter®. STATISTICAL ANALYSIS The parameters were compared and analyzed using post hoc tests for stability and prefer- ence. Independent sample t-test was for effi cacy evaluation. Signifi cance was set at a con- fi dence level of 95%, and data were expressed as mean ± standard error. RESULTS AND DISCUSSION The tonic base formulation was developed by variation of humectant (glycerine and bu- tylene glycol) content, as shown in Table I. All of the tonics were clear, colorless liquids that remained stable following centrifugation assay. Thereafter, accelerated stability tests were performed using repeated heating–cooling cycles, and higher pH was observed in all of the formulations. Preferences for the hair tonics were examined for spreadability, skin absorption, greasiness, color, and odor. Tonic C gained the highest preference for spread- ability, skin absorption, and greasiness, but preferences for color and odor were compa- rable. An increase of humectant contents was found to reduce the scores of all preference criteria. Therefore, hair tonic base C was further developed into green tea hair tonic. Various proportions of green tea extract (2–7%), delineated by the reported facial sebum reduction (13–15), were incorporated into base C using butylene glycol (Table II). The increased content of the extract did not affect the product pH (p 0.05) and all of the green tea hair tonics remained stable.