In vivo confocal Raman microscopic determination of depth profiles of the stratum corneum lipid organization influenced by application of various oils

•Intercellular lipids order profile measured by confocal Raman microscopy in vivo.•Topically applied oils influence the intercellular lipids order in stratum corneum.•Oils do not permeate through the stratum corneum in vivo.•Plant-derived oils influence deeper-located layers more than mineral-derived oils. The intercellular lipids (ICL) of stratum corneum (SC) play an important role in maintaining the skin barrier function. The lateral and lamellar packing order of ICL in SC is not homogenous, but rather depth-dependent. This study aimed to analyze the influence of the topically applied mineral-derived (paraffin and petrolatum) and plant-derived (almond oil and jojoba oil) oils on the depth-dependent ICL profile ordering of the SC in vivo. Confocal Raman microscopy (CRM), a unique tool to analyze the depth profile of the ICL structure non-invasively, is employed to investigate the interaction between oils and human SC in vivo. The results show that the response of SC to oils’ permeation varies in the depths. All oils remain in the upper layers of the SC (0–20% of SC thickness) and show predominated differences of ICL ordering from intact skin. In these depths, skin treated with plant-derived oils shows more disordered lateral and lamellar packing order of ICL than intact skin (p0.1), except plant-derived oils at the depth 30% of SC thickness. In the deeper layers of the SC (60–100% of SC thickness), no difference between ICL lateral packing order of the oil-treated and intact skin can be observed, except that at the depths of 70–90% of the SC thickness, where slight changes with more disorder states are measured for plant-derived oil treated skin (p