The Relationship Between Photoallergens And Melasma

Objective:To study the relationship between common photoallergens and melasma, meanwhile provide an evidence for the relationship between sun exposure and melasma.Methods:Based on the standard procedures of photopatch test recommended by British Photodermatology Group(BPG),15 photoallergens were selected from the national cosmetics photosensitive dermatitis diagnostic criteria,and 5 suspicious photoallergens were selected from national cosmetics dermatitis diagnostic criteria, photopatch tests were performed on 50 patients with melasma and 30 healthy volunteers without melasma.Result:24 out of 50(48.0%) patients suffered from melasma had positive result in the phtopatch test,on the contrary,this figure was 7 out of 30(23.33%) in the control group,the positive rate in melasma patients was higher than the control group,the difference was significant with p-value＜0.05.In melasma patients,3 photoallergens (PABA,sulfanilamide and thiourea),and 3 suspicious photoallergens (thiomersalate,niekel sulfate and bichromate potassium) had higher reaction rate; paraphenylenediamine,p-hydroxybenzcic acid mixture,lemon oil,cinnamaldehyde,colophonium and oleum santali had no reaction. Conclusion:The positive rate in photopatch tests in melasma patients was obviously higher,photoallergens and melasma were related;and hardly detectable postimflammatory hyperpigmentation which induced by contacting photoallergens repeatedly might account for the pathogenesis of melasma.