j. Soc. Cosmet. Chem., 28, 83-87 (February 1977) Preservation of cosmetic lotions with imidazolidinyl urea* plus parabens WILLIAM E. ROSEN and PHILIP A. BERKESutton Laboratories Inc., Roselle, N.J. 07203. THOMAS MATZIN and ARTHUR F. PETERSON Wells Laboratories, Inc.,Jersey City, N.J. 07306. Received February 27, 1976. :' Synopsis A model cosmetic LOTION containing 0.2 per cent METHYLPARABEN plus 0.1 per cent PROPYL- PARABEN was previously shown to be unsatisfactorily preserved because it failed to kill Pseudomonas (P.) aeruginosa. Addition of 0.3 per cent IMIDAZOLIDINYL UKEA to the lotion gave an Imidazolidinyl Urea- !i:.' PARABEN PRESERVATIVE SYSTEM, which was effective against both an initial challenge of P. ae- ruginosa and two rechallenges. INTRODUCTION The evaluation of cosmetic lotion preservation using pure and mixed microbial culture challenges has been reported by the CTFA Microbial Preservation Subcommittee (1). In a study describing the results of challenging a "model" lotion with both pure and mixed cultures, the Subcommittee concluded that both types of challenge tests are valid, but that the information from pure culture tests can be "a valuable aid in reformulating borderline preservative systems." The Subcommittee used two modifications of a model lotion (2) for evaluation, as shown in the following table taken from their report (1). *Germall 115, registered trademark of Sutton Laboratories, Inc., Roselie, New Jersey 07203. 83

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.