Ergot derivatives are chemical compounds derived from the fungus Claviceps purpurea, primarily infecting cereals like rye. Ergotism, poisoning from consuming cereals contaminated with these derivatives, historically associated with severe symptoms, including hallucinations, convulsions, and vascular issues. Ergot derivatives, especially the alkaloid ergotamine, cause blood vessel constriction, leading to circulatory issues. Historically, ergotism, linked to consuming contaminated bread, was associated with outbreaks known as “St. Anthony’s Fire.” Despite toxic effects, ergotamine found medical applications, notably in migraine treatment, although its use is now limited. Weather conditions and plant variety influence contamination. Modern agricultural practices and quality controls minimize risks, while research explores medical applications of ergot derivatives.