Regional analysis of ceramides within the stratum corneum in relation to seasonal changes.

We studied the regional variations and seasonal changes of ceramide quantities in the stratum corneum of human skin. In summer, the total lipid amounts extracted from the stripped stratum corneum were highest in the forehead, followed by the chest and upper back, with the lowest level in the sole of the foot. In winter, while the total lipid distribution followed the same trend as that in summer, the absolute amounts slightly decreased, especially in the forehead and chest, as compared with those found in summer. Ceramide analysis showed that while a higher level was seen in the cubital fossa in summer, the level was highest in the forehead during winter. A seasonal comparison of ceramide mass revealed a slightly increased level in winter compared with summer, at almost all sites tested, except in the cubital fossa and dorsum pedis, reflecting seemingly enhanced keratinization in winter. These findings indicate that in young adults, the mass of ceramide remains steady at similar levels at various skin sites, providing maintenance of a pertinent water reservoir and the barrier function of the stratum corneum, even under different seasonal conditions.