84 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Ingredients Lotion A Lotion B (Unpreserved) (Preserved) Per cent w/w Per cent w/w 1. Lanolin Alcohol* 6.0 6.0 2. Acetylated Lanolin•' 2.0 2.0 3. Stearic Acid XXX 2.0 2.0 4. Glyceryl Monostearate--Acid Stable 2.0 2.0 5. Sodium Lauryl Sulfate (100 per cent) 1.0 1.0 6. Magnesium Aluminum Silicates 0.5 0.5 7. Methylparaben -- 0.2 8. Propylparaben -- 0.1 9. Propylene Glycol 5.0 5.0 10. Water (deionized) 81.5 81.2 (The first four items in the above table constitute the oil phase and the remaining items, the water phase). Lotion A, which had a pH of 5.6, was prepared without any preservative. Lotion B, which had the same pH, contained a preservative system of 0.2 per cent methyl- paraben plus 0.1 per cent propylparaben. Both lotions were challenge tested by the participating laboratories in the Subcommittee's study with pure cultures of the follow- ing organisms (1): Escherichia (E.) coli, ATCC 11229 Pseudomonas (P.) aeruginosa, ATCC 13388 (QMB 1468) Staphylococcus (S.) aureus, ATCC 6538 and Candida (C.) albicans, ATCC 10231. When challenged with approximately 106 organisms/ml, Lotion A killed S. aureus within 7 days, but failed to kill the other 3 microorganisms. Lotion B, which contained both methylparaben and propylparaben, killed E. coli, S. aureus, and C. albicans, but failed to kill P. aeruginosa, which remained at high levels throughout the 28-day study period. The Subcommittee noted that "both test solutions were considered to be un- satisfactorily preserved, although it is clear that Lotion B was better preserved than Lo- tion A" (1). METHODS Since the parabens alone were not capable of adequately preserving this lotion, the:ill authors decided to test the effect of adding Imidazolidinyl Urea at a level of 0.3 cent to Lotion B, to give "Lotion B Modified." The pH of"Lotion B Modified" was 5.6, the same as that of Lotion B. The detailed procedure for challenge testing with P. aeruginosa 13388 and evaluation by the quantitative pour plate count was described previously (1). All plate counts reported in Table I were carried out in triplicate. The efficacy and capacity of the pre- servative system was further tested by rechallenging the lotion two more times. week after the initial challenge, sampling was done on the total sample. One-third of the sample was retained for further sampling, and the remaining two-thirds was *Amerchol L- 101, registered trademark of Amerchol, Edison, New Jersey 08817. 'l-Modulan, registered trademark of Amerchol, Edison, New Jersey 08817. SVeegum, registered trademark ofR. T. Vanderbilt Co., Inc., New York, N.Y. 10017.

PRESERVATION OF COSMETIC LOTIONS Table I A 85 Result of Challenge of Lotion B with P. aeruginosa (Control Run) Time after Challenge Pseudomonas Plate Count 0 days 5.6 x l0 s 1 day 6.8 x l0 s 2 days 5.4 x 106 7 days 7.1 X 10 6 14 days 8.4 x 106 21 days 8,2 x 10 6 28 days 6.6 x 106 B Results of Challenge of"otion B Modified" (Lotion B plus Imidazolidinyl Urea) with P. aeruginosa Time after challenge 0 day 1 day 2 days 7 days 14 days 21 days 28 days Time after first rechallenge 7 days 14 days 21 days 28 days Time after second rechallenge 7 days 14 days 21 days 28 days Pseudomonas Plate Count 4.0 x lO s 1.3 x 10 = 0 0 0 0 0 challenged again with P. aeruginosa. This was sampled 1 week later and then subdivided ß into 2 portions. One portion was retained for further sampling, and the remaining por- tion was challenged again (a third time) with P. aeruginosa. All challenged samples were subcultured at 1, 2, 3, and 4 weeks. All were stored at room temperature. .? RESULTS Challenge testing confirmed that Lotion B failed to kill P. aeruginosa, which continued :: to grow vigorously over the 28-day test period in spite of the presence ofparaben pre- servatives. In contrast, Lotion B Modified did kill P. aeruginosa within 2 days, and continued to show the absence ofP. aeruginosa throughout the 28-day test period (see Fig. 1 and Table I). Counts of"0" in Table I are actually "10 organisms/ml," and are, therefore, plotted as 10 • in Fig. 1.) : ..