LAVENDER OIL/WATER/STABILIZER SYSTEMS 441 (lO) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) S. E. Friberg, Q. Yin, and P. A. Aikens, Vapor pressure of phenethyl alcohol and limonene in systems with water and Laureth 4, Int. J. Cosmet. Sci., 20, 355-367 (1998). S.E. Friberg, M. Szymula, L. Fei, P. A Aikens, J. Barber, and A. A1-Bawab, Vapor pressure of a fragrance during evaporation in simple emulsion, Int. J. Cosmet. Sci., 19, 259-265 (1997). Y. Tokuoka, H. Uchiyama, and M. Abe, Phase diagrams of surfactant/water/synthetic perfume ternary systems, Colloid. Po/ym. Sci., 272, 317-323 (1993). Y. Tokuoka, H. Uchiyama, M. Abe, and S. D. Christian, Solubilization of some synthetic perfumes by anionic-nonionic mixes surfactant systems, Langmuir, 11, 725-729 (1995). Y. Satio, K. Miura, Y. Tokuoka, Y. Kondo, M. Abe, and T. Sato, Volatility and solubilization of synthetic perfumes by pluronic, J. Dispers. Sci. Techno/., 17, 567-576 (1995). J. Yang, G. Rong, S. E. Friberg, and P. Aikens, The phase behaviour of polyoxyethylene 10 stearyl ether/geraniol/olive oil/H20 system and preliminary evaluation of fragrance evaporation, Int. J. Cosmet. Sci., 18, 43-56 (1996). Z. Zhang, S. E. Friberg, and P. Aikens, Change of amphiphilic association structures during evapo- ration from emulsions in surfactant-fragrance-water systems, Int. J. Cosmet. Sci., 22, 181-194 (2000). D. Thracharod and K. P. Rao, Transdermal absorption of nifedipine from miceoemulsions of lipophilic skin penetration enhancers, Int. J. Pharm., 11,235-240 (1994). S.J. Vona, Jr., s. E. Friberg, and A.J. Brin, Location of fragrance molecules within lameliar liquid crystals, Col/olds Surf A, 137, 79-89 (1998). S. E. Friberg, Fragrance compounds and amphiphilic association structures, Adv. Colloid Interface Sci., 75, 181-214 (1998). S. E. Friberg, L. Fei, and P. A. Aikens, Vapor pressures of organic solvents in amphiphilic association systems, Recent Res. Develop. Phys. Chem., 1, 193-208 (1997). S. E. Friberg, Vapor pressure of some fragrance ingredients in emulsion and microemulsion formula- tions, Int. J. Cosmetic Sci., 19, 75-86 (1997).

j. Cosmet. Sci., 54, 443-449 (September/October 2003) The 21-day human cumulative irritation test can be reduced to 14 days without loss of sensitivity JAMES P. BOWMAN, RICHARD S. BERGER, and OTTO H. MILLS, Hill Top Research Inc., P.O. Box 429501, Cincinnati, OH 45242 ALBERT M. KLIGMAN and TRACY STOUDEMAYER, S.K.I.N., Inc., 151 East Tenth Avenue, Conshohocken, PA 19428. Accepted for publication May 16, 2003. Synopsis The 21-day cumulative irritation test for assessing the irritancy of topical products and chemicals is a venerable procedure that appears to have become the gold standard for manufacturers. Berger and Bowman in 1982 (1) showed that reducing the exposure to 14 days was less traumatic to the volunteers, less costly, less arduous, and did not affect reliability or the capacity to place the test agents in the proper rank order of irritancy. In the current study we compared (a) the 21-day cumulative irritation test, (b) the 14-day cumulative irritation test, and (c) the 14-day test with every-other-day patching. Additionally, ten-day, seven-day and four-day data from the 21-day test were compared. Forty-one subjects completed this study of six test materials. Two sets of patches were applied to each subject's lower back. One set had 21 consecutive applications of the test articles. The second set was applied, and removal of the test articles occurred Monday, Wednesday, and Friday for 14 days. The 21-day test fully differentiated the test materials from each other. Using only the first 14 days of the 21-day test also fully differentiated the test materials. Every-other-day patching rank ordered the test materials the same as the everyday patching, but full differentiation of the test materials was not obtained. We conclude that the 14-day cumulative irritancy test is as reliable and sensitive as the 21-day test, along with the obvious advantages in time, cost, and minimization of trauma to the test subjects. INTRODUCTION The 21-day cumulative irritation test is a demanding and onerous procedure that poses a hardship to the volunteers as well as being costly and time-consuming. The aim of the present study was to confirm the results of a prior study that showed that reducing the time to 14 days did not result in loss of sensitivity or reliability. MATERIALS AND METHODS The procedure is a modification of that described by Lanman (2,3). Two sets of patches were applied to each subject's lower back. Nineteen-mm Hill Top Chambers © were used 443