HUMAN CUMULATIVE IRRITATION TEST 449 utilizing data from the first 14 days of the 21-consecutive-day patch data. Analyses performed using data from the first four days, the first seven days, and the first ten days of the 21-consecutive-day patch data and the data obtained from the every-other-day patching, while not differentiating each and every test material, did rank order the test materials in the same manner. The ability of data obtained through the 14-consecutive- day patch design to differentiate each test material as successfully as data obtained from the 21-consecutive-day patch design confirms the earlier results of Berger and Bowman (1). The conclusions arrived at in this study reconfirm that a reduction in the expense, time, and trauma associated with conducting cumulative irritation studies is possible and is strongly recommended for future studies. REFERENCES (1) R.S. Berger and J.P. Bowman, A reappraisal of the 21-day cumulative irritation test in man, J. ToxicoL Cut. Ocular ToxicoL, 1, 109-115 (1982). (2) B. M. Lanman, E. B. Elvers, and C.J. Howard, The role of human patch testing in a product devel- opment program, Joint Conference on Cosmetic Sciences, The Toilet Goods Association (currently The Cosmetic, Toiletry and Fragrance Association), Washington, DC, April 21-23, 1968. (3) L. Philips, M. Steinberg, H. I. Maibach, and W. A. Akers, Comparison of rabbit and human skin response to certain irritants, Toxicol. AppL PharmacoL, 21, 369 (1972). (4) W.J. Conover, Practica/Nonparametric Statistics (John Wiley & Sons, New York, 1980), pp. 299-305.

j. Cosmet. Sci., 54, 451-462 (September/October 2003) O/W microemulsion as a vehicle for sunscreens M. EUGENIA CARLOTTI, MARINA GALLARATE, and VALERIA ROSSATTO, Dipartimento di Scienza e Tecnologia del Farmaco, Universit,3 degli Studi di Torino, via Giuria 9 (M. E. C., M.G.), and Dipartimento di Chimica Analitica, Universita degli Studi di Torino, via Giuria 5 (V.R.), 10125 Turin, Italy. Accepted for publication June 16, 2003. Synopsis In recent years, transparent dispersions or diluted milks have been used as sunscreens. These products contain water-soluble sunscreen agents, and quite frequently are washed away from the skin. However, O/W microemulsions are now being prepared as transparent vehicles for sunscreens. They are waterproof, non- sticky, and easily spreadable. The microemulsions are prepared by using pseudoternary diagrams, by combining lipids with surfactant blends and a polar phase. Soya lecithin and decylpolyglucose produce transparent systems with the lowest percentage of surfactants. These microemulsions contain 4-methylbenzilidene camphor or octylmethoxy- cinnamate as sunscreen agents. Cyclomethicone, menthol, and allantoin give products a good skin feel, and stearyl methicone gives the waterproof effect. These systems show a Newtonian flux. Little permeation of the sunscreens' trough lipophilic and hydro- philic membrane is evidenced. INTRODUCTION At present the formulations of sunscreens is subjected to many technical and legislative requirements (1,2) that restrict the choice of materials and of UV sunscreens. The stability of the sunscreens is influenced not only by their molecular structure, but also by the vehicle (3). For good efficiency, the vehicle, the adhesion to the horny layer, and the possible percutaneous resorption must be investigated. In recent years, transparent dispersions or diluted milks have found wide application as sunscreens such products contain water-soluble sunscreen agents, which are frequently washed off from the skin, no longer providing protection against rash and sunburn (4-9). This study aims to demonstrate the preparation of transparent, nonsticky, easy-spreading, water-proof sun- screens, which can be supplied with a mechanical diffuser. O/W microemulsions were chosen as transparent systems having a sufficient amount of lipid phase to dissolve Address all correspondence to M. Eugenia Carlotti. 451