Histamine release in immediate-type hypersensitivity reactions in intact human skin measured by microdialysis. A preliminary study

The purpose of this study was to evaluate the application of a microdialysis technique for measurement of interstitial histamine levels in intact human skin. Three allergic subjects were investigated. Single dialysis fibers were glued to nylon tubings and inserted in forearm skin by means of a fine cannula. Dialysis fibers were inserted in triplicate and perfused with isotonic saline at a rate of 3 microliters/min. After a period of 2 h a 60-microliters base-line period was established. Then the patients were skin prick tested (SPT) with allergen in duplicate and a single saline control. Dialysate was collected in consecutive 30 microliters fractions. Histamine concentration in the dialysate was analyzed with a glass fiber fluorescence assay. Median base-line histamine level was 4 (range 4-7) ng/ml. Following allergen SPT, dialysate histamine concentration increased to 81 ng/ml (74-128), with maximum values 10-20 min after SPT. Intraindividual coefficient of variation on peak histamine levels was 18.9%. No histamine increase was seen following saline SPT. We consider microdialysis to be a valuable method for assessment of allergic mechanisms in intact human skin.