The impact of surface loading and dosing scheme on the skin uptake of fragrances

• The article describes an in vitro study of the skin uptake of fragrances.
• The correlations between fractional uptake and loading differ between fragrances.
• The mass uptake of fragrances is not necessarily additive at all loadings.
• These effects reflect the interactions between fragrances and skin barrier lipids.
• They can distort the exposure-based estimates used in risk assessment and diagnostics.

This study compared the skin uptake of γ-undecalactone, decanol, and dodecyl acetate in an in vitro, un-occluded penetration assay in which they were applied to porcine skin at different finite loadings and application schemes. The pattern of fractional uptake differed between the chemicals and did not show the often assumed inverse correlation with surface loading. Furthermore, the mass uptake of identical cumulative amounts of the chemicals was not always additive. These results show that the uptake of fragrances in absence of occlusion and at finite loadings is chemical-specific and depends on the surface loading, the application scheme, and most probably, on the effects of the chemicals on the skin barrier efficiency. The observed lack of additivity might explain some of the differences in the responses observed in patch and repeated open application tests, and the boosting of the allergic state in sensitized individuals by sub-clinical exposures.

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