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.) : ..

86 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 10 7 _ 10 6 _ 10 5 • 10 4 • 10 3 10 2 lO 1 Lotion B Lotion B Modified 0 1 2 7 14 21 28 Days Figure 1. P. aeruginosa as challenge organism: test product Lotion B versus Lotion B modified As can be seen from Table I, Lotion B Modified satisfactorily met the second challenge and the third challenge with P. aeruginosa, and no pseudomonads were detectable over the 28-day test period. SUMMARY Lotion B, containing 0.2 per cent methylparaben and 0.1 per cent propylparaben, was inadequately preserved. When 0.3 per cent Imidazolidinyl Urea was added to Lotion B, the Imidazolidinyl Urea-paraben preservative system was effective against both the initial challenge ofP. aeruginosa and two rechallenges.