[Tar treatment of psoriasis].

Tar is generated by dry distillation of coal or wood. Crude coal tar, tar extracts or refined tar products are used for therapy. Tar exerts an antipsoriatic effect by reducing cell proliferation. This effect is enhanced when tar is applied in combination with UV irradiation. The phototoxic reactions induced by several tar components in combination with UV-A cannot be employed for therapeutic purposes, since the painful smarting reaction prevents the application of the large UV-A doses required for therapy. Tar applied together with anthralin has recently been found to decrease the irritative qualities of anthralin. Due to the potential carcinogenic properties of tar, uncontrolled applications are to be avoided.