Skin is exposed to solar lights and suffer from the harmful effects of UV lights. It has been speculated the possibility that sebum which is peroxidized by UV lights, damages the stratum corneum. Then, to clarify influence of the peroxidized-sebum on skin conditions, we examined the relationship between physiological parameters of skin and peroxide-scavenging activity of corneocytes. The measurements of parameters and the collection of corneocyte were carried out on cheek of females which were aged from 23 to 37 years. The peroxide-scavenging activity was estimated by quantification of the remaining t-butylhydroperoxide (BHP) after incubating with corneocytes. The remaining BHP was quantified with dihydrorhodamine 123-peroxidase technique. The subjects which possessed the lower activity of peroxide scavenging in corneocytes, showed the decreases of corneocyte-area and the increases of TEWL. These findings suggested the possibilities that peroxides altered the barrier function of the intercellular lipid bilayers, and caused the abnormal differentiation of epidermis.