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.

PRESERVATION OF COSMETIC LOTIONS 87 REFERENCES (1) J. A. Rogers, G. Jacobs, E. M. Owen, D.C. Pease,Jr., A. F. Peterson, W. H. Riley, A. G. Schenkel, J. L. Smith, C. E. Stegmann, andJ. A. Ramp, CTFA Cosmet. J, 5, 2-7 (1973). (2) Amerchol Laboratory Handbook, p. 56, column 1.