JOURNAL OF COSMETIC SCIENCE 328 the mean MEDUW. This strongly suggests that the determination of two MEDs is unnecessary that and one should be eliminated. Eliminating one of the two MED deter- minations would increase the benefi t/risk ratio of the COLIPA sunscreen water resistance effi cacy testing without harm to effi cacy. While this would not benefi t the millions of sunscreen users, it would benefi t the subjects in the clinical trial. METHODOLOGY Multiport solar simulators (Solar Light Company, Philadelphia, PA) are maintained by the Metrology Department at Consumer Product Testing Company, Inc. Data from 59 subjects were generated from 150-W multiport solar simulators data from 48 subjects were generated from 300-W multiport solar simulators. The MED, the minimum amount of energy required to produce a uniform, clearly demar- cated erythema response in each subject, was determined according to COLIPA method- ology (1). In the COLIPA methodology, 15 to 30 minutes after application the test sites are immersed in water for 20 minutes, dried for 15 minutes, immersed again for 20 min- utes, and then air dried for 15 minutes or until completely dry before UV exposure. RESULTS In testing sunscreens using the COLIPA guidelines, this testing facility has generated 107 MEDUS and MEDUW on identical subjects. For the 107 subjects, the means of the MEDUS and MEDUW are identical: MEDUS MEDUW Mean 21.0 mJ 21.0 mJ STDEV 0.55 mJ 0.61 mJ In 106 cases, the MEDUS equaled the MEDUW. In only one of 107 instances did the MEDUS not match the MEDUW, and in that instance the MEDUS was slightly higher. From this data, we conclude that the MEDUS is equivalent to the MEDUW. Because the MEDUS and MEDUW are equivalent, we propose that determination of the MEDUW be eliminated from the COLIPA guidelines for SPF testing. The MEDUW serves no useful purpose and increases the exposure of the subject to UV radiation. CONCLUSION Data from 107 subjects shows that water immersion does not alter the minimal erythema dose because there is no difference between the MEDUS and MEDUW. Thus, the MEDUS and MEDUW as required by the COLIPA method for water- resistant sunscreen testing are redundant and unnecessary. Eliminating the MEDUW would increase the benefi t/risk of the clinical trial while maintaining quality in test methodology.

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