J. Soc. Cosmet. Chem., 48, 141-149 (May/June 1997) Comparison of three detergents using the patch test and the hand/forearm immersion test as measurements of irritancy P. CLARYS and A. O. BAREL, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium. Accepted for publication July 31, 1997. Synopsis Two anionic surfactants and a nonionic surfactant were tested in two different irritation test protocols. The two anionic surfactants differed in the number of ethoxylations. The latter is known to influence the mildness properties of the detergents. The irritation test protocols used were a patch test procedure (two repetitions) and a hand/forearm immersion procedure (three repetitions) that is much closer to real user conditions. Skin irritation was quantified using bioengineering methods. The patch test procedure delivered a clear rank order for the test products: the anionic surfactant with two ethoxylations was found to cause a more severe irritation compared to the anionic surfactant with seven ethoxylations, and the nonionic surfactant was the mildest. The hand/forearm immersion test provoked a much weaker irritation, making the discrimination between the products less obvious. A moderate-to-good correlation was obtained when comparing the product rank order obtained in the two protocols. INTRODUCTION The patch test on human volunteers is a widely used in vivo method for the evaluation of the irritant properties of detergents. However, this procedure is susceptible to several experimental factors influencing the outcome of the results in a significant way. Indeed, the literature reports on the type of chamber used (1), the temperature of application (2), the concentration of the detergent used (3), etc. When taking into account these ex- perimental factors, the patch test method is known to be a reproducible test procedure. The objective quantification of different skin parameters, through instrumental readings characterizing the irritation, increased the value of the patch test procedure (3-4). Nevertheless, the conditions of the patch test are far from the conditions under which the products are normally used. Hence, several test procedures were developed that are closer to real user conditions (5). It was demonstrated that procedures like the hand/ forearm immersion test equally require a high standardization of experimental condi- tions in order to assure reproducibility (6). Only a few studies have compared the irritant properties of detergents using both the patch test and a procedure close to domestic user conditions (7). It was our aim to 141

142 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS evaluate the irritant/mildness properties of different detergents (anionic and nonionic) in the same population using the patch test procedure and the hand/forearm immersion test. It is known that the irritation/mildness properties of anionic surfactants are influ- enced by the number of ethoxylations in the chemical structure (8). We compared two anionic surfactants with a different number of ethoxylations (two and seven, respec- tively), as well as a nonionic detergent in a patch test procedure and a hand/forearm immersion procedure. Instrumental determination of skin parameters such as TEWL, skin color, and stratum corneum capacitance were used for the objective quantification of the irritative response (4). METHODS VOLUNTEERS Fifteen Caucasian subjects (mean age 21.4 + 2.9 years six women and nine men) participated in the study. They all had normal skin and were not undergoing any medical treatment. Informed consent was given by each volunteer, and the study was approved by the ethical committee of our university. PRODUCTS Three products were evaluated: two anionic tensides (Texapon N28 © and Texapon ASV ©) and one nonionic tenside (Plantaren 1200©). Product 1 (Texapon N28) is a sodium lauryl ethersulfate, containing two ethoxylations in its chemical structure. It is used in many cosmetic preparations. Product 2 (Texapon ASV) is a polyethylene sodium lauryl ethersulfate it contains seven ethoxylations and is often used in shampoos. Prod- uct 3 (Plantaren 1200) is a lauryl polyglycoside. This nonionic substance is often used as a co-tenside. All products were furnished by the same company (Henkel, Dusseldorf, Germany). The detergents were tested at a concentration of 2% in distilled water. PATCH TEST PROTOCOL Patches were applied to six delimited skin areas of the volar part of the forearms (9). Due to regional differences in irritation potential, a randomization procedure was used (10). Prior to any treatment, baseline skin parameters were determined (see Instruments, below). Products were applied by means of Hill Top © chambers (Hill Top Research Inc., Miamiville, Ohio) containing 150 lal of the test solution. The chambers were sealed to the skin using a self-adhesive fabric (Mephix ©, Mi51nycke, Sweden). As a control, an empty chamber, a chamber containing 150 lal of distilled water, and an untreated skin area were included. Patches were applied a first time for 24 hours and a second time for 21 hours. Between the two applications the skin areas were left untreated for three hours. Skin parameters characterizing the irritation were evaluated prior to the second application of the patches. After removal of the patches, the test sites were rinsed using tap water and dried with a soft towel. Skin parameters were determined again at 3, 24, and 48 hours after removal of the second set of patches.