Irritation and staining by dithranol (anthralin) and related compounds. IV. Visual estimation of erythema compared with contact thermometry and laser Doppler flowmetry.

Irritation and staining caused by equi-irritant doses of dithranol (anthralin) and 10-butyryl dithranol (butantrone) were observed for one week after a single 24-hour exposure under occlusion. The test chambers were applied on the uninvolved dorsal skin of 11 psoriasis patients. The estimates of erythema were made with a refined reading scale, and to test the visual discriminatory power they were compared with objective measurements of contact temperature and blood flow of the skin. A sensitive thermistor and a novel laser Doppler flowmeter were used. On the whole, erythema, contact temperature and superficial blood flow, as interdependent parameters of cutaneous inflammation, all showed a time-dependent statistically significant correlation to the dose of dithranol and 10-butyryl dithranol. The intercorrelations between erythema and blood flow and between erythema and temperature were statistically significant, too. With the doses used, staining of the skin did not hamper the measurement of superficial blood flow, but it did exaggerate visual estimates of erythema at the 4th and 7th day readings.