Comparison between three detective methods of sun protection factor for sunscreen in vivo

Abstract

Objective To investigate the three methods for sun protection factor determination in vivo in Chinese under the same condition, and to evaluate the feasibility and reliability of the three methods. Methods There were 45 healthy volunteers in Guangzhou area were involved in the study. All of them were randomly divided into three groups. Among them 15 volunteers were in the current method group, 5 volunteers in the simplified method group, and 25 volunteers were in the single-exposure method group. Two standard sunscreens of SPF 4 and SPF 15 and one sunscreen labeled as SPF 20 were tested by all the three methods in the study. Two experienced observers read results, respectively, under the same conditions. Results The volunteers in the current method group received the largest dose of UV light.The simple method was next to it and the single-exposure reduced 4-5 folds of UV dose received. The results of the two observers in the current method group and the single-exposure group were very close. But the test results of P3 were not completely coincident between the two observers in the simplified method group. SPFs value of the three sunscreens were 4. 12, 16.09, and 22.60 obtained by the observer 1 and 4. 18, 15.92, and 21.97 obtained by the observer 2, respectively. In the simplified method group, SPFs values of ＜4, ＞15, ＞20 and ＜4, ＜15, ＞20 were obtained by the two observers. In the single-exposure method group, SPFs values of the three sunscreens were 4.04, 15.34, 21.33 by the observer 1 and 3. 96, 15.82, 21.33 by the observer 2, respectively. Conclusion The single-exposure method is convenient and easily to operate and may replace the current method some day. The simple method is not valuable in determination of SPF labeled on the packages of sunscreens, but may be useful in supervision of the market sunscreen products. Key words: Sun protection faction value; Sunscreens; Determination in vivo