['Skin maceration is recognized as a risk factor for the development of certain skin lesions. In health care settings, incontinence-associated skin maceration is highly prevalent in the elderly. However, the effect of senescence on maceration has not been fully elucidated.', 'To reveal the enhancement of the maceration-induced ultrastructural alteration and barrier function of the epidermis by aging.', 'Skin maceration was reproduced by exposure to agarose gel in human and rat. The ultrastructural alterations in human and rat tissue were observed by transmission electron microscopy. The skin barrier function was evaluated by noninvasive methods in human, and by the transdermal penetration of small- and large-fluorescent molecules in rat. In order to reveal the effect of aging on the skin maceration, we compared these parameters between young and aged rats.', 'In macerated skin, we observed expansion of the interstices of the stratum corneum, spinosum, and basale of the epidermis; disruption of the intercellular lipid structure in the stratum corneum; a decreased number of cell processes in the stratum spinosum and basale. The transdermal penetration test in the rat using two types of fluorescein indicated that maceration disrupted skin barrier function. Furthermore, senescence-enhanced ultrastructural and functional alterations were revealed in the rodent studies.'] Does aging enhance maceration-induced ultrastructural alteration of the epidermis and impairment of skin barrier function?