Clobetasol-17-propionate (CP) and crude coal tar (CT) have an anti-inflammatory potential. Both agents have been advocated to suppress irritation of the skin during dithranol treatment. The effect of CP and CT on dithranol-induced irritation was studied by the assessment of erythema and measurement of alkaline phosphatase (ALP) as a direct reflection of the metabolic activity of the endothelial cells. Dithranol was applied for 2 h in the relatively high concentration of 10%, which resulted in a marked inflammation of the skin in all volunteers. Neither CP nor CT influenced the erythema. In contrast, CP and CT had a synergistic effect on the dithranol-induced induction of ALP. In conclusion, the present study indicates that CP and CT are not indicated for the treatment of dithranol-induced irritation.