Claviceps purpurea is a microscopic fungus that may parasitize almost all types of grains (except corn). It is used in medicine to collect certain alkaloids that it produces during its development. These substances may be used to create antihypertensive medications. Lysergic acid derived from claviceps purpurea is a precursor involved in the manufacture of LSD. However, consumption of grains infected by claviceps purpurea may cause serious afflictions, notably ergotism, a disease characterized by circulatory troubles that can eventually lead to necrosis of the extremities.