j. Soc. Cosmet. Chem., 82, 153-161 (May/June 1987) Evaluation of subjective irritation induced by soap materials M. B. FINKEY, The Dial Technical Center, Scottsdale, AZ 85254. Received January 21, 1986. Synopsis A sensory questionnaire was employed to determine the subjective irritation perceived by subjects partici- pating in clinical irritancy studies comparing pairs of bar soaps. The questionnaire consisted of a seven- point category scale for the attributes of dryness, tightness, itching, and burning/stinging. The question- naire allowed for detection of significant differences between soaps as described by these attributes. There was no strict relationship between erythema and self-perceived irritancy when any pair of treatments was compared, nor was there a consistent correlation among any of the attributes evaluated for any single soap bar. The questionnaire provided a simple, economical method for assessing subjective irritancy in conjunc- tion with a clinical evaluation. INTRODUCTION Characterization of the irritation potential of personal care products generally includes a series of animal tests followed by human tests. Animal testing may include primary skin and primary eye irritation studies. Human testing may include 21-day cumulative irritation, various patch tests, or exaggerated use and normal use studies (1). There has been increasing awareness and concern among manufacturers of cosmetics and personal care products over what is termed subjective irritation. This is a perceived burning, stinging, itching, drying, or tight feeling or other discomfort in the absence of any visible irritation, i.e., erythema and/or edema. In the past, this type of response was generally ignored or only detected through consumer irritation complaints. How- ever, consumers usually do not take the time to correspond with manufacturers and instead will stop using a product if not satisfied. Most work with sensory perceived attributes of personal care products is based on adap- tation of the food texture profile method (3). The texture profile method gives the sensory description and a quantitation of various textural qualities of food products during the successive stages of initial feel, biting, and swallowing by using a highly trained panel. Schwartz (4) applied this technique to train a panel to evaluate and quantify product attributes of female facial cosmetics. The majority of published work has been done with products that are not rinsed off, such as lotions and cremes (4-6). Usually positive attributes such as smoothness, softness, and suppleness are evaluated. Subjective irritation can be induced in sensitive individuals with certain chemicals such as DMSO, lactic acid, urea, and alcohol. Kligman investigated the phenomenon of 153

154 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS stinging and based a test on this observation (2). Preselected sensitive subjects were brought to an actively sweating state and test substances were applied to their nasolabial folds. The subjects evaluated the perceived stinging sensation using a four-point scale with "0" equivalent to no stinging and "3" equivalent to severe stinging. Kligman also evaluated the irritancy in terms of clinically produced erythema following occlusive patch testing of a series of test materials. Results demonstrated little correlation be- tween clinical irritancy and the subjective response of stinging. Little work has been done regarding sensory perceived attributes of soap products. Frosch (7) briefly described the use of a subjective scale in conjunction with washing tests using soaps. The forearm or face was washed with a soap two times daily. The skin response was graded in terms of erythema and discomfort. A four-point discomfort scale was used with a "1" equivalent to slight tightness and a "4" equivalent to severe pain. In this test, the discomfort scores appeared to correlate with the erythema scores. It was our intention to gather more information regarding consumer perception of sub- jective irritation as it relates to clinical irritancy of soap materials. The most appropriate type of test to gather such panelist-generated data under controlled conditions appeared to be paired comparison exaggerated use studies. Data were generated in conjunction with facial irritation studies. MATERIALS AND METHODS FACIAL IRRITATION Subjects. Approximately 15 subjects participated in each study. Age, race, and sex of each was documented. Medical records of each subject were screened. Those with histo- ries of skin disorders such as eczema or psoriasis or with systemic conditions such as diabetes were eliminated. Subjects exhibited no erythema on the upper cheeks at the initial evaluation. Cremes, lotions, and other cosmetic products were restricted on the specified sites throughout the study. Subjects were directed to limit outdoor activity throughout the study. Subjects had not participated in similar studies for at least six weeks previously. PROCEDURES Complexion bars, bars targeted for use by the entire family (all-family bars), and syn- thetic detergent bars were compared in the four studies conducted. Two test materials were compared in each study. For each subject, one product was randomly assigned to one cheek while the remaining product was assigned to the remaining cheek. Ten percent aqueous (tap water, 0 ppm hardness) solutions of commercially purchased bars were prepared daily with the aid of heat. The solutions were maintained as liquids in a 50øC water bath. Subjects reported to the laboratory three times daily for a five-day period for supervised washings. The time intervals between the three daily sessions were two and three hours. An experienced technician conducted the washings. An absorbent rayon cosmetic square (Coets, Personal Products, Inc.) was moistened with 3.0 ml of test solution. A l•-diam - eter circular area on the upper cheek, as demarcated by a plastic template, was washed with a circular motion for 30 seconds. The solution was left on the cheek for an addi-