The roughness of lip skin is related to the ceramide profile in the stratum corneum

Objective The structure of skin on the lips is different from skin at other areas of the body; the water content of the stratum corneum (SC) and the barrier function there is low. Therefore, the lips can easily become dry and rough. The SC plays an important role in the barrier and water-holding functions of the skin. Above all, ceramides (CERs) are important SC lipids which maintain SC functions. The purpose of this study was to clarify the relationship between the degree of lip roughness and the CER profile. Methods Forty-one Japanese female subjects with normal skin (age range 22–52 years; mean 34.1) were enrolled in this study. The degree of lip roughness was scored, the values of capacitance and transepidermal water loss (TEWL) were measured and CER profiles of the SC were analysed using tape-stripping. Results The degree of lip roughness was related to the capacitance values but not the TEWL values. The roughness level correlated with the levels of CER[NH], CER[NP], CER[AH], CER[EOS] and CER[EOH] and the average carbon numbers of CER[NDS], CER[NH] and CER[NP] but not with the level of total CERs. The capacitance values of the lips were related not only with the levels of total CERs but also with the levels of CER[NH], CER[NP], CER[AH], CER[AP], CER[EOS], CER[EOH] and CER[EOP] and with the average carbon numbers of CER[NDS], CER[NS], CER[NH] and CER[NP]. The TEWL values of the lips were related not only with the levels of total CERs but also with the levels of CER[NH], CER[AH], CER[AP], CER[EOS] and CER[EOH]. Conclusion The relationship between lip roughness and the CER profile was clarified for the first time. The results suggest that not only the level of total CERs but also the specific CER species and their carbon numbers affect the maintenance of SC function.