Time course and intensity of anthralin inflammation on involved and uninvolved psoriatic skin.

Anthralin inflammatory oedema was measured using Harpenden calipers on psoriatic plaque and clinically uninvolved skin 6-48 h after anthralin application. There was a highly significant reduction in oedema response on the psoriatic plaque compared with the uninvolved skin (P less than 0.001). Both sites produced a maximal oedema response at 24 h. These results do not support the theory that the decreased anthralin reactivity of psoriatic plaque is due to the high levels of arachidonic acid found in involved psoriatic skin.