Safety Evaluation of 2-Aza-8-oxohypoxanthine by in Vitro Skin Sensitization and Human Tests

2-Azahypoxanthine (AHX) is a compound isolated from the agaricomycete Lepista sordida that forms fairy rings and 2-aza-8-oxohypoxanthine (AOH) is a metabolite of AHX in plants. In the present study, we assessed the safety of AOH for cosmetic applications via in vitro skin sensitization tests and human skin sensitization, phototoxicity, and photosensitization assays. In the tests, AOH did not induce skin sensitization in both human cell line activation test (h-CLAT) and KeratinoSensTM methods. AOH also did not induce human dermal phototoxicity or photosensitivity. Moreover, in repeat insult patch tests, the compound did not induce any human skin reaction. Hence, we conclude that AOH is safe as a cosmetic ingredient. To the best of our knowledge, this investigation is the first to evaluate the safety of AOH on human skin.