Is Ergot Poisonous? The Dangers of the Claviceps Fungus

January 2, 2026 •

4 min read

Historically, severe epidemics of a deadly ailment known as 'St. Anthony's Fire' affected thousands of people in Europe during the Middle Ages, with the cause ultimately traced to ergot. This fungal growth, which develops on cereal grains like rye, contains potent toxic alkaloids, confirming unequivocally that ergot is poisonous.

Quick Summary

Ergot, a fungus that infects cereal crops, produces highly toxic alkaloids that can cause a severe condition known as ergotism in humans and livestock. The effects range from convulsions and hallucinations to gangrene and even death. The toxicity arises from consuming contaminated grains like rye, though modern agricultural practices have made human poisoning rare.

Key Points

Ergot is a Toxic Fungus: The fungus Claviceps purpurea contains highly poisonous alkaloids that can cause severe illness or death if ingested.
Ergotism has Two Forms: Poisoning, or ergotism, can manifest as either gangrenous (causing limb loss due to restricted blood flow) or convulsive (leading to neurological symptoms like seizures and hallucinations).
It Has a Dark History: In the Middle Ages, mass poisonings were known as 'St. Anthony's Fire' and may have influenced historical events like the Salem witch trials.
Modern Controls are Effective: Today, regulations and advanced grain cleaning have made human ergot poisoning extremely rare in most developed countries.
Livestock are Still at Risk: Animal feed can become contaminated, posing a risk of poisoning to livestock, especially pregnant or young animals.
Ergot has Medical Applications: Some ergot-derived compounds are used in controlled doses for prescription medications, particularly for migraines and to control bleeding after childbirth.

Ergot, the hardened fungal body or sclerotium of species in the genus Claviceps, is a highly toxic natural contaminant that primarily affects cereal grains such as rye, wheat, and barley. The danger comes from the potent ergot alkaloids produced by the fungus, which have profound and harmful effects on both human and animal health. Though large-scale human epidemics are now rare due to modern farming and processing techniques, the risk of poisoning remains, especially for livestock.

The History of Ergotism: St. Anthony's Fire

For centuries, ergot poisoning, or ergotism, caused immense suffering and death across Europe, with outbreaks often shrouded in mystery. In the Middle Ages, it was known as 'St. Anthony's Fire' due to the burning sensation in the limbs experienced by victims. Monks of the order of St. Anthony would care for the afflicted, and surprisingly, many patients improved simply because they were no longer eating the contaminated rye bread that formed a staple of their diet.

Historical and Cultural Impacts

The strange and terrifying symptoms of ergot poisoning led to many historical interpretations and folklore. Symptoms like hallucinations, convulsions, and psychotic behavior have led some historians to suggest ergotism could have played a role in events like the Salem witch trials of 1692, where the erratic behavior of some villagers might be attributed to the fungus. The 'Dancing Plague' of 1518, where people compulsively danced and convulsed for days, is another historic event some scholars link to ergot poisoning. The medical community did not formally identify the cause until the 19th century, thanks to the work of mycologist Louis Rene Tulasne.

The Mechanisms of Ergot Poisoning

The toxic alkaloids within the ergot fungus act on the mammalian central nervous system and vascular system by mimicking natural neurotransmitters like dopamine and serotonin. This interference is what causes the wide array of symptoms seen in ergotism. The toxicity can manifest in two distinct clinical forms:

Convulsive Ergotism: This form affects the central nervous system and is characterized by painful seizures, spasms, diarrhea, and a crawling sensation on the skin known as formication. It can also cause hallucinations, mania, or psychosis.
Gangrenous Ergotism: This is the result of ergot alkaloids causing sustained vasoconstriction, or narrowing of the blood vessels, particularly in the extremities. This cuts off blood supply, leading to numbness, extreme pain, tissue death, and ultimately, the loss of limbs.

Ergot and Modern Medicine

In a unique paradox, specific ergot alkaloids have been isolated and synthesized for use in modern medicine, albeit in highly controlled dosages. For example, ergotamine is used to treat severe migraine headaches, while ergometrine is used in obstetrics to control postpartum bleeding. However, misuse, overdose, or adverse drug interactions can lead to a modern form of ergotism.

Comparison of Ergotism Symptoms: Historical vs. Modern


Feature	Historical Ergotism (Medieval)	Modern Ergotism (Accidental/Drug-Induced)
Cause	Accidental consumption of contaminated grains (rye bread)	Overdose of ergot-derived medications (e.g., for migraine)
Onset	Often long-term, chronic exposure through diet	Can be rapid (acute) or chronic depending on dose
Main Symptoms	A mix of convulsive and gangrenous symptoms	Predominantly vasoconstrictive symptoms leading to gangrene
Associated Factors	Poor sanitation, reliance on contaminated crops, cold/wet weather	Drug interactions (e.g., with HIV medication), kidney/liver disease
Likelihood Today	Extremely rare due to modern grain cleaning	Very low with proper medical supervision, but possible

Preventing Ergot Contamination

Today, the risk of ergot poisoning in humans is minimized by stringent food safety regulations and advanced grain processing. However, farm animals, particularly livestock that consume screenings from grain milling, can still be affected. Prevention methods primarily focus on agricultural practices.

Strategies to Reduce Ergot Risk

Crop Rotation: The fungus rarely survives in soil for more than one year, so rotating away from cereals for a season can reduce the fungal load.
Deep Plowing: Burying crop residues and ergot bodies to a depth of at least four centimeters can impede their germination.
Mowing/Grazing Wild Grasses: Keeping field borders free of wild grasses before they flower prevents these alternative hosts from harboring the fungus.
Seed Cleaning and Sorting: Advanced technology is used to clean and sort grains, effectively removing the dark, hard ergot sclerotia before processing into food or feed.
Proper Storage: Storing grains at low temperatures (<5°C) and controlled humidity can minimize the epimerization process that affects alkaloid activity.

Conclusion

To answer the question, "Is ergot poisonous?" the answer is a resounding and historical "yes". The fungus Claviceps purpurea and its associated alkaloids have a long and devastating history of causing disease in both humans and livestock, known as ergotism. While modern agricultural practices and food safety standards have largely relegated human ergot poisoning to the history books in most developed nations, its potential for harm remains relevant, particularly in agricultural and medical contexts. The powerful pharmacological effects of its alkaloids, which can cause severe vasoconstriction and neurological symptoms, highlight the delicate balance between a substance's therapeutic potential and its inherent toxicity. Awareness of its past impact and continued vigilance in food production are essential to ensure this historical plague remains a rarity.

Frequently Asked Questions

Ergot is a fungal pathogen, primarily Claviceps purpurea, that infects grains and grasses. It forms dark, hardened structures called sclerotia that replace healthy kernels and contain highly toxic alkaloids.

Ingesting ergot leads to a condition called ergotism. Symptoms can include gangrenous effects like numbness and loss of limbs, or convulsive effects such as hallucinations, seizures, and psychosis, and can be fatal.

In developed countries, human ergot poisoning is very rare due to strict agricultural standards and effective grain cleaning. However, it can still affect livestock, and poisoning can occur from misuse of ergot-derived medications.

No, cooking does not destroy the toxic ergot alkaloids. Contaminated grains must be removed before milling or processing, as the toxins remain potent even in baked products.

It was called 'St. Anthony's Fire' in the Middle Ages because of the agonizing, burning sensation experienced by victims in their limbs, which was caused by the fungal toxins constricting their blood vessels.

Rye is particularly vulnerable to ergot infection because it is an open-pollinated crop, making it more accessible to fungal spores. Other susceptible crops include wheat, barley, and some forage grasses.

Diagnosis depends on symptoms but can involve physical exams, angiography (to check for constricted blood vessels), and toxicology tests. Treatment involves discontinuing exposure to the toxin and managing symptoms, potentially with medications or surgery for gangrene.

Farmers can prevent contamination by using crop rotation, deep plowing to bury ergot bodies, controlling wild grasses around fields, and planting clean, certified seeds.