pH AND SKIN 333 pH 5.9 solution at 60 and 90 minutes for the pH 7 solution at 30, 60, and 90 minutes and for the pH 7.5 solution at 180 minutes. DISCUSSION In our earlier studies, we were able to show that the water content of the horny layer is higher in older than in younger subjects, showing also higher variability for the former (2). In the present study, the infrared spectroscopic results confirmed the earlier find- ings. The corneometric skin capacitance measurements showed the same tendency, albeit outside the level of statistical significance. The present studies further show that the application of a specific detergent multicomponent emulsion leads to an initial, transient hydration effect. This hydration effect proved to be largely independent of the pH value of the solution nor was their any clear dependence on the age of the subjects. The dehydrative effect of detergent substances is well known. Blank and Shappirio (1) were able to demonstrate that the water-binding capacity of the stratum corneum decreases after the application of detergent substances. In earlier studies (3), we showed that both a soap solution and a surfactant solution caused a considerable dehydration of the stratum corneum. These studies involved infrared spectroscopy measurements as well as corneometric determinations of skin capacitance. These earlier findings appear to be corroborated by the present results. No exhaustive study on the dependence of the dehydrative effect of detergent solutions on their pH exists in the literature. In the older literature, it was often presumed that soaps had rather a moisturizing effect while synthetic surfactants had a dehydrative effect. Our earlier studies (3) have already disproved this concept. The present studies demonstrate that the dehydrative effect of this particular slightly alkaline detergent emulsion can be more pronounced than that of the same composition at neutral or slightly acid pH. If this result is generally applicable, slight acidification of detergent solutions would be a reasonable strategy to minimize dehydrative effects. This possi- bility should be explored in more depth. A notable aspect of the present study was the difference between the groups of older and younger subjects. Although the dehydrative effect was apparent as a tendency in both groups, it was more pronounced among the younger subjects than among the older subjects. REFERENCES (1) I. H. Blank and E. B. Shappirio, The water content of the stratum corneum. 3. Effects of previous contact with aqueous solutions of soaps and detergents. J. Invest. Dermatol., 25, 391-401, 1955. (2) M. Gloor, G. Hirsch, and W. Willebrandt, On the use of infrared spectroscopy for the in vivo measurement of the water content of the horny layer after application of dermatological ointments. Arch. Derre. Res., 272, 305-313, 1981. (3) M. Gloor, M. Gehse, and E. W/51fle, Beeinflussung der Hornschichtfeuchtigkeit durch waschaktive Substanzen. ,•rztl. Kosmetol., 15, 293-302, 1985. (4) K. Mosler, Hautfeuchtigkeitsmessung--kein Problem mir dem Corneometer 420. Pao c. Kosmet., 64, 375-379, 1983. (5) R. Osberghaus, D. Gloxhuber, H. G. Van Raay, and S. Braig, Hydragen F, ein neuer Hautfeuchtigkeitsregulator--Methoden und Ergebnisse des Wirkungsnachweises. J. Soc. Cosmet. Chem., 29, 133-146, 1978. (6) W. Schneider, Seifen und Syndets, •sth. Med., 10, 304-311, 1961. (7) H. Tronnier, Differenzierte Feuchtigkeitsmessung an der menschlichen Haut, •rtzl. Kosmetol., 10, 281-308, 1980.

j. Soc. Cosmet. Chem., 42, 335-340 (September/October 1991) In vitro absorption of butylated hydroxyanisole through human skin REGINA SCHUMANN, Max von Pettenko•r-Institut, Bundesgesundheitsamt, Thielallee 88-92, D~1000 Berlin 33, Germany. Received February I, 199 I. Synopsis The absorption of butylated hydroxyanisole (BHA) from an ointment and its permeation through human skin were measured in vitro. Following the application of 0.07% BHA in a commercial water-in-oil ointment and a continuous skin contact of 16 h, 2.68% of the amount applied had penetrated into the receptor fluid (mean rate 0.18 •g BHA/1.77 cm2/16 h). Measurable amounts of BHA were found in the horny layer, and up to 50% of the applied dose had penetrated into the epidermis/dermis. It is concluded that BHA may also be absorbed under regular use conditions in vivo. INTRODUCTION Butylated hydroxyanisole [2(3)-tert.-butyl-4-hydroxyanisole] (BHA) is being used as an antioxidant not only in the human diet but also in cosmetics (1). Its use as a food additive is generally regarded as safe, and the Joint FAO/WHO Expert Committee on Food Additives (2) has set up an acceptable daily intake of up to 0.5 mg/kg body weight. Cosmetic products may contain up to 0.07% BHA, added mainly to prevent oxidation of lipid ingredients. However, due to the lack of information on its percu- taneous absorption, it is difficult to evaluate the amounts of systemic intake of BHA after dermal application. This study was designed to measure the absorption of BHA from an ointment through human skin using an in vitro method. To simulate a day-long skin contact of a cosmetic product and to make sure that steady-state diffusion was established, the absorption was measured over a period of 16 h on excised whole-thickness skin without occlusion. EXPERIMENTAL MATERIALS Human abdominal skin was obtained 24 hours post mortem and immediately trans- ported to the laboratory. The skin was stored in a refrigerator and used within 12 hours. The subcutaneous fat was carefully removed with a scalpel. Each portion of skin, derived 335