146 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II Stratum Corneum Capacitance (arbitrary units) as Measured Before and at Different Time Intervals in the Patch Test Procedure and the Hand/Forearm Immersion Procedure, Respectively Patch test Immersion test Time Water N28 ASV Plantaren Water N28 ASV Plantaren 0 64+8 64+9 66_+9 65+9 68+6 70+7 68+5 68+6 1 58 + 10 60+ 11 55 +8 53 +6 73 +7 66+ 5 68+6 73-+7 2 59+7 61+ 10 55 + 13 49+6 71-+8 67 +9 68+7 71+9 3 62 +7 57 + 11 61+ 10 56-+ 5 65 +5 59+9 63 +9 65 + 5 4 64+5 35 + 15 54+8 53-+ 11 69+5 65 +5 69+6 69+ 5 MANOVA s. s. s. s. n.s. n.s. HAND/FOREARM IMMERSION TEST Besides differences in baseline values, similar kinetics were obtained when comparing the reactions on the hand with those on the forearm. As a consequence, we will only discuss the results measured on the forearm. Compared to the patch test, the irritation response was less pronounced in the hand/forearm immersion test. The TEWL values, as measured during and after the immersion protocol, showed a trend to increase as a function of the number of immersions (see Table I). This trend was noticed for the different detergent solutions. A weak increase in function of the number of immersions was equally noticed for the immersion in water alone. For the immersion in water alone, a return to baseline values was noticed within 24 hours after the last immersion. Statistically, no differences were detected between the different kinetics. When analyzing the global response (YWEWL), only a weak increase was detected after immersion in the different detergent solutions compared to immersion in water alone (see Table IV). Hydration kinetics showed a more pronounced decrease after immersion in the N28 solution compared to ASV and Plantaren solution (see Table II). Lowest values were measured eight hours after the third immersion. The kinetics of the N28 was found to be significantly lower compared to immersion in water alone. The decrease caused by the other products was not statistically significant. Table III a* Skin Color (arbitrary units) Value as Measured Before and at Different Time Intervals in the Patch Test Procedure and the Hand/Forearm Immersion Procedure, Respectively Patch test Immersion test Time Water N28 ASV Plantaren Water N28 ASV Plantaren 0 6.3 + 1.5 6.1+ 1.4 6.0+ 1.4 6.2 + 1.3 6.1+ 1.2 6.5 + 1.4 6.3 + 1.5 6.3+ 1.4 1 7.7 + 1.2 9.3 + 1.5 8.1 _+ 1.6 8.7 + 1.3 6.5 + 1.4 6.6 + 1.4 6.5 + 1.3 6.5 + 1.5 2 7.4 _+ 1.6 11.1 + 3.2 9.0 + 1.9 8.6 + 1.7 6.6 + 1.6 6.8 _+ 1.2 6.6 + 1.2 6.8 + 1.7 3 7.3 + 1.2 12.6 + 1.6 10.0 + 2.0 8.8 + 1.1 6.8 + 1.4 6.9 + 1.6 6.7 -+ 1.2 7.1 _+ 1.5 4 7.1 + 1.4 11.1 + 1.6 8.9 + 1.5 8.2 _+ 1.2 6.7 + 1.1 6.7 + 1.1 6.8 + 1.1 6.8 + 1.2 MANOVA s. s. s. n.s. n.s. n.s.

TWO TESTS OF DETERGENT IRRITANCY 147 Table IV Global Response to the Different Products as Calculated for the Patch Test Procedure and the Hand/Forearm Immersion Procedure, Respectively ETEWL (g/m2/h) EHyd (a.u.) Ea* (a.u.) Product Patch Immersion Patch Immersion Patch Immersion Water 59 -+ 9 66 + 11 318 _+ 32 357 + 25 33 -+ 6 34 + 6 N28 194 + 53* 71 + 19 265 _+ 36* 329 + 20* 50 _+ 6* 33 ñ 6 ASV 123 + 34* 71 _+ 18 292 + 33* 335 +- 20 42 _+ 7* 33 ñ 6 Plantaren 99 +- 22* 70 + 12 277 _+ 25* 348 + 24 41 +_ 5* 34 + 7 (*) indicates that values differ significantly from testing with water alone. (a.u.) = arbitrary units. The global response (Y'Hyd) showed similar trends, with a significant difference only for immersion in the N28 solution compared with immersion in water alone (see Table IV). These lower capacitance values point to the dehydration side effect of the N28 solution. Concerning the a* color value, we noticed a trend toward an increase only after the different immersions (see Table III). Here again we found a slight increase after im- mersion in the tank containing water without detergent. In contradiction with the other skin parameters, Plantaren was found to be the detergent causing the greatest color changes. Analysis of the global response (5',a.) did not reveal any significant differences (see Table IV). COMPARISON BETWEEN THE TWO PROTOCOLS Regression of the global parameters obtained after the patch test and the immersion test delivered a correlation coefficient ofr = 0.839 for the (ZTEWL), r = 0.776 for (Y'Hyd), and r = 0.400 for (5',a.), respectively. DISCUSSION Reactions in the patch test were more pronounced compared to the reactions in the hand/forearm immersion test. The long contact time during the patch procedure, in an occlusive way, seems to affect skin integrity more severely than repetitive short immer- sions. Prolonged occlusion of the skin surface results in decreased barrier properties due to an accumulation of water in the stratum corneum (1) and due to increased tempera- ture under the patch (1,14). During prolonged exposure to the detergent solutions, the intercellular lipids may be perturbed (15). As a result, the irritant substances can easily penetrate towards the deeper skin layers, where they can elicit an irritation. As suggested by several authors, irritant reactions are mainly caused by surfactant-protein interaction in the deeper skin layers (15). Apparently these penetration-promoting conditions are not present in the hand/forearm immersion test, resulting in a weaker response after the three immersions. When considering the different products tested, regardless of the protocol used, it becomes clear that N28 had more irritation potential than the two other substances. The irritant character of N28 was clearly demonstrated in the patch test protocol by the strongly increased TEWL values, the decreased hydradon values, and the high a* values.