EVALUATING IRRITATION POTENTIAL 293 Table III Summary of In Vivo Results Product Irritation (%) A 74 B 91 C 110 D 150 E 170 F 290 Results are expressed as a percentage of the mild control. they ranged from the mild to the extremely irritating. The formulas of two of the products are proprietary to Colgate-Palmolive. Table I lists the ingredients of the test products. 250 • 200 l o 150 .•.• lOO ß ß ß r =0.92 p = 0.01 I I I I I I I 25 30 35 40 45 50 55 60 65 Collagen Swelling (% of 1% SLS) Figure 1. Correlation between the effect of antibacterial liquid soaps on collagen swelling, expressed as a percentage of the effect of 1% SLS, and on the in vivo results, expressed as a percentage of the effect of the mild control.

294 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 1 Ii r = 0.71 p = 0.11 0 I I I I I I 0 1 2 3 4 5 6 7 In Vitro Ranking Figure 2. Correlation between the ranking of antibacterial liquid soaps using collagen swelling and the ranking of antibacterial liquid soaps using the modified soap chamber test. IN VITRO METHODS Collagen swelling test. The collagen swelling test was adapted from the method of Blake- Haskins et al. (1). In brief, a piece of collagen sheet (1 cm 2) from Colla-Tec (Plainsboro, NJ) is incubated for 24 hours, at 50øC, with a solution of the finished product at 1% of the dry extract at its own pH. The collagen is weighed before and after incubation to determine the amount of swelling. The more the collagen swells, the more irritating the product. The results are expressed as follows: CSW = (weight after incubation - initial weight)/initial weight pH rise test. In the pH rise test (2), equal volumes of a solution of bovine serum albumin (Sigma, St. Louis, MO) at 2% (w/v) and a pH of 5.6 and a solution of the finished product at 2% of the dry extract and a pH of 5.6 are incubated for one hour at room temperature. The resulting solution contains the finished product at a 1% concentra- tion. The pH of the solution is measured after incubation. The higher the pH rises, the more irritating the product. The results are expressed as follows: pH rise = pH after incubation - 5.6