Circadian and ultradian (12 h) variations of skin blood flow and barrier function in non-irritated and irritated skin-effect of topical corticosteroids.

The skin is the organ that receives the greatest exposure to light and shows a high-amplitude circadian rhythm in epidermal cell proliferation. We have previously demonstrated that the skin barrier function has a significant circadian rhythm. Corticosteroids (CS) are the most commonly used topical treatment in dermatology. Time-dependent differences in their efficacy and side-effects would be of considerable interest. The aims of the current study were to examine time-dependent cycles in the effect of topical CS application in healthy and irritated skin on skin blood flow and its relationship to barrier function. Twenty clinically healthy, diurnally active subjects were examined at eight and nine time points over a 24 or 28 h span respectively, using non-invasive skin bioengineering techniques of laser Doppler imaging, a transepidermal water loss (TEWL) device and a skin thermometer in a 28 h session. The results of this current study demonstrate circadian and ultradian (12 h) variations in skin blood flow. A significant correlation was found between skin temperature and skin blood flow but not with TEWL. Circadian and ultradian rhythms are maintained during treatment with high-potency and mid-potency CS in healthy skin. These rhythms persist during stratum corneum disruption with and without CS application.