EFFECTS OF AGE ON IRRITATION RESPONSES 215 Due to test subjects being sensitized to test article I (OXY 10 benzoyl peroxide van­ ishing cream), the statistical analysis was conducted with this article removed. RESULTS The distribution of the 26 test subjects in each group is shown in Table III, and test articles were rank ordered as shown in Table IV. The test articles were essentially rank ordered the same. Allowing for variation in a biological test should explain the flipflop in the rank ordering of test articles B and D, which were the fourth and fifth, and fifth and fourth, most irritating materials in Group 1 and Group 2, respectively. OVERALL ANALYSIS COMP ARING GROUPS The analysis of variance indicated no significant difference between groups (p=O. 1) ! 0) and no interaction of groups and test articles (p = O.4259). A summary of the overall analysis of variance is shown in Table V. Age 25-29 30-39 40-45 Rank 1 2 3 4 5 6 7 8 Table III Distribution of Test Subjects Group 1 (18--45) Group 2 (65-80) n Age 3 65-69 13 70-75 10 76-80 Table IV Rank Order of Test Articles Group 1 (18--4 5) Group 2 (65-80) Test article Test article means Rank Test article G (DOAK, AHA facial day cream) 24.7 G (DOAK, AHA facial day cream) A (0.2% SLS) 22.0 2 A (0.2% SLS) K (Carmol 10) 11.0 3 K (Carmol 10) B (0.1 % benzalkonium chloride) 10.2 4 D (0.1 % Retin A cream) D (0.1 % Retin A cream) 8.7 5 B (0.1 % benzalkonium chloride) H (Lachydrin 12 lotion) 6.7 6 H (Lachydrin 12 lotion) F (75% propylene glycol/distilled 7 F (75% propylene glycol/distilled water) 3.0 water) C (50% xylenes/petrolatum) 0.8 8 C (50% xylenes/petrolatum) 9 J (Lacticare lotion) 0.6 9 J (Lacticare lotion) 10 E (50% isopropyl 10 E (50% isopropyl myristate/petrolatum 0.3 myristate/petrolatum) n 13 9 4 Test article means 22.6 21.8 10.6 7.7 7.0 6.2 1.9 0.7 0.6 0.3

216 JOURNAL OF COSMETIC SCIENCE Table V Overall Analysis of Variance Overall mean Group 1 (18--45) Group 2 (65-80) 8.81 7.95 n = 26 per group. The p-value for the group effect was 0 .1510, indicating no significant difference between groups. COMPARISON OF TEST ARTICLES FOR EACH GROUP The Friedman analysis indicated significant differences between test articles for each group (p 0.001). Both groups differentiated the most irritating test articles (G and A) from the remaining samples test article K differentiated from those less irritating test articles test articles B, D, and H differentiated from samples F, CJ, and E and test article F separated from test articles C, J, and E. A summary of these analyses is shown in Table VI. ANALYSIS BY TEST ARTICLE Additional analyses were conducted evaluating for differences between groups for each test article separately. There were no significant differences between groups for the Table VI Comparision of Test Articles for Each Group Group 1 (18--45) Group 2 (65-80) Test article G A K B D H F C J E Significant comparisons at p 0.05 Test article means* 24.7 22.0 11.0 10.2 8.7 6.7 3.0 0.8 0.6 0.3 G,A VS K,B,D,H,F,C,J,E K vs B,D,H,F,C,J,E B,D, vs H,F,C,J,E H vs F,C,J,E F vs C,J,E Test article G 22.6 A 21.8 K 10.6 D 7.7 B 7.0 H 6.2 F 1.9 C 0.7 J 0.6 E 0.3 Significant comparisons at p 0.05 * Test article means joined together are not significantly different. Test article means* G,A VS K,B,D,H,F,C,J,E K vs D,B,H,F,C,J,E D vs B,H,F,C,J,E B,H vs F,C,J,E F vs C,J,E