Angelicin psoriasis drug, molecular model. This drug is used to treat psoriasis, a chronic disease which causes red scaly patches to appear on the skin. These patches, or plaques, are inflamed areas of excessive skin cell production. Angelicin (and other drugs belonging to the furocoumarin family) is given orally or applied to the skin in the presence of ultraviolet A radiation, in a process known as phototherapy. This combination disrupts the overproduction of skin cells. Angelicin occurs naturally in some plants of the Apiaceae family, including Garden Angelica (Angelica archangelica). Atoms in this model are represented by coloured spheres; carbon is green, hydrogen is white and oxygen is pink.