Postural skin colour changes during the corticosteroid blanching assay.

To assess the effect of the position of a limb (dependency) on the cutaneous vasoconstrictor (blanching) assay (VCA) using topical corticosteroid preparations. Two studies were performed on the forearms of healthy volunteers using tristimulus reflectance colorimetric assessments. The first one conducted in 60 normal adults aimed at quantifying the range of variation in the skin chromaticity a* when the arm was successively positioned horizontally and vertically, either in the upward or downward direction. In the second study, 16 volunteers were selected according to a weak spontaneous postural dependency of the limb in a* (<2 units). The blanching effect of 0.1% mometasone furoate, 0.1% betamethasone valerate and petrolatum were compared to the colour of an untreated site. Chromaticity a* and the colorimetric variable (DeltatL*(2) + Deltata*(2))(0.5) were measured in time following a 2-hour application. The postural variations in skin colour varied among subjects. The majority of them (80%) presented a difference in a* higher than 2 units between the upright and downward arm positions. The upright position appeared to be the most sensitive to show significant differences in the VCA. Mometasone furoate exhibited the most prominent effect, significantly higher than betamethasone valerate and controls. The corticosteroid VCA is influenced by the position of the limb. The upright position increases the sensitivity of the test. Mometasone furoate is more potent than betamethasone valerate.