Fagopyrum sagittatum (buckwheat), furocoumarin in Ammi majus (bishop’s weed), Cymopterus spp. (spring parsley, wild carrot, various clovers, alfalfa and brassicas) and perloline in Lolium perenne (perennial ryegrass). Ingestion of these plants in active growth can cause primary photosensitisation.
Secondary or hepatogenous photosensitisation occurs when liver cells are damaged, for example, in hepatitis or biliary duct obstruction. Phylloerythrin, an end product of chlorophyll metabolism normally excreted in the bile, is then liberated into the bloodstream and accumulates in the tissues to cause photosensitisation. Plants respon- sible for hepatotoxic damage and secondary photosensi- tisation include bog asphodel (Narthecium ossifragum), Lupin spp. (Lupinus), Lantana spp. (Lantana) and panic grass spp. (Panicum). Various fungi can be responsible, for example, Pithomyces chartarum, which contains sporidesmin, is found in perennial ryegrass (L. perenne) and is the cause of facial eczema in New Zealand sheep (big head or geeldikop in South Africa). Certain chemicals such as phenothiazine, carbon tetrachloride and corti- costeroids may also induce photosensitisation.
The lesions of photosensitisation are confined to the white