Variations of skin sensitivity to intracutaneous histamine provocations with regard to provocation time.

Dermal provocation tests with histamine and other mediators of allergy are widely used as diagnostic tools and as clinical pharmacological models. Diurnal variations of skin reactivity e.g. flare reactions have been postulated earlier. Potential differences in skin reactivity using histamine provoked flare areas as model were investigated by means of five different placebo formulations (i.v. solution; p.o. solution; p.o. solid forms). Flare reactions have been provoked every 3rd hour within a time span of 29 h using a cross-over design with an H1-antagonist positive control. No provocation was provided between 0:00 and 7:00 a.m. There was no statistically significant variation of skin reactivity with respect to provocation times under placebo treatment conditions. No dependence on plasmacortisol levels was observed. Interindividual differences in skin reactivity are more pronounced than the intraindividual variations.