Laser Doppler evaluation of skin reaction in volunteers after histamine iontophoresis

Iontophoresis was used for a non-invasive administration of the agonist histamine. Flares and weals areas were measured after 1%, 0.01% and 0.0001% histamine solution iontophoresis (30 s, 1.4 mA/cm2). There was no clear-cut correlation between area and concentration. 0.0001% histamine solution iontophoresis induced only a vanishing redness. When a typical weal developed ( 1% and 0.01% histamine), the blood perfusion was lower at histamine administration site between 10 and 40 min as compared to the values recorded during the same time interval in the flare area. When the flare disappeared, the level of laser Doppler flowmetry (LDF) at the weal site still remained higher than basal values. The higher the histamine concentration, the higher the LDF values at flare sites. Controls indicated that only a low and transient increase in LDF values was observed after NaC1 iontophoresis (30 s, 1.4 mA/cm 2) and that histamine application ( 1%, 30 s) did not modify basal blood perfusion. Therefore, we suggest to use 1% histamine iontophoresis (30 s, 1.4 mA/cm 2) to induce skin reaction to the agonist and to characterize the increase in skin blood perfusion using a laser Doppler velocimeter.