The Unassuming Cereal Fungus in Bread That Haunted Europe for Centuries and Paved the Way for LSD

Have you ever encountered ergot? I hope not, for your good health… Indeed, this little-known fungus is responsible for a rare disease today, ergotism. Rare, but deadly! It has caused the death of millions of people over the centuries and terrorized an entire village in 1951. This ergot even made it possible to discover a well-known drug, LSD. So how can such a small fungus cause so much damage?

Rye ergot, primarily a cereal parasite

Before becoming a drug, ergot is first a mushroom, by its nickname Claviceps purpurea Tulasne. It is a parasite of cereals, and more particularly of rye.

More specifically, ergot refers to a certain part of the fungus, called the sclerotium. This blackish-colored growth has a hook shape. It recalls the specific claws of rooster legs, which are called “dewclaws”. Rye ergot corresponds to the form of resistance of the fungus when the bad season comes. It is therefore a phase of the life cycle of the fungus.
In cereals, the sclerotium will settle on the plant and end up replacing the grains. In case of heavy infestation, up to 30% of the grains can be replaced by dewclaws.

These fungi therefore have an impact on the harvest, because they cause damage to the plant. However, it is particularly the health consequences that are problematic.
Indeed, ergot contains toxic substances which can trigger a serious disease, ergotism.

Ergot is a fungus parasitic on cereals, which contains a toxin dangerous to humans and animals.
Credits: Shutterstock/Ritvars

>> Also read: Archaeology: people have been eating cereals since the Stone Age

Ergotism, a fatal disease

Ergot is not only dangerous for plants. It can also poison animals and humans, so it is a poisonous mushroom.

These are chemical substances, contained in ergot, which are toxic and which cause ergotism disease. It is not an infectious and contagious disease, but rather a poisoning. Most of the time, we get sick when we eat bread made with infested cereal flour.

The disease can present in two forms. The first is rather acute and convulsive and impacts the central nervous system. It corresponds to strong intoxication.
The second form is slower and affects skin tissues. It can progress to gangrene, that is to say the death of tissues due to a cessation of their vascularization. This slow form contracts rather during weak but prolonged intoxication.

In the acute form, people may experience seizures, painful spasms, headaches, as well as diarrhea and vomiting. Often these symptoms are also accompanied by hallucinatory delusions.
In the gangrenous form, toxic substances will lead to vasoconstriction of the blood vessels. This slows down or even eliminates the irrigation of certain tissues. The extremities of the limbs, such as the fingers or toes, are particularly affected.

The outcome of the illness is not always fatal, despite everything, several people succumb to it, sometimes by committing suicide, as the hallucinations are so prevalent. Furthermore, in the case of the gangrenous form, when the tissues are dead, there is no other choice than to amputate.

>> Also read: Halloween: watch out for bitter gourd poisoning!

The fire of Saint-Antoine

Although it took time to identify ergot as the cause of ergotism, the disease is clearly not new. It has wreaked havoc several times throughout history.

It was already described as early as the 5th century BC, detailing its characteristic symptoms. A burning body, attacked extremities… The idea of ​​“burning and devouring fire” often comes up in historical writings.
Indeed, the gangrenous form begins with itching which quickly transforms into a sensation of intolerable heat. Gangrene occurs a few days later, giving a blackened appearance to the tissues. These burning sensations and this black color of the flesh give ergot another nickname, “plague of fire”.

This gangrenous form so traumatized medieval Europe that it led to the creation of a hospital monastic order in the 19th century: the order of the Antonines. We actually link illness to Saint Anthony, because his attribute is fire. These monks thus make it their mission to treat people suffering from this “Saint Anthony’s fire”.

And it works! For two reasons… Firstly, because people who can, when they go on pilgrimage to the monastery, move away from the place of contamination. Then, because the monks have developed an effective remedy. Small breads… with wheat flour! The sick therefore heal because they are no longer in contact with the toxin. From there to speak of a miracle…

An episode caused trouble in 1951… We then spoke of the “Cursed Bread Affair”. That summer, several series of food poisonings hit France, but the most serious affected the small town of Pont-Saint-Esprit, in Gard. Poisoning caused 7 deaths, 50 internments in psychiatric hospitals and 250 sick people.

Justice condemns the Union Meunière du Gard, responsible for the sale of flour contaminated with ergot. However, a much less probable theory, but still supported by some today, would incriminate the CIA, the famous American agency. Indeed, in the 1950s, several agencies from different countries wanted to test the effect of substances contained in ergot as an incapacitating chemical weapon.

>> Also read: Plague of Justinian: ancient DNA finally reveals the real pathogen of the first pandemic

A toxin that gave birth… to LSD

Ergot, as has been said, contains toxic chemicals. More precisely, these are alkaloids, molecules of plant origin. Some of these compounds will be used as medications, particularly in obstetrics, to prevent hemorrhages after childbirth. Other substances will serve as medications against migraines.
However, for some time now, the European Medicines Agency has considered that the benefit/risk balance of medicines based on ergot derivatives is no longer favorable. They therefore recommend that doctors review the treatments prescribed to their patients.

And finally…chemicals from ergot will produce LSD, a very powerful hallucinogenic drug. It causes intense sensory changes, hallucinations and a more or less marked loss of reality. Its consumption can thus cause anxiety, panic attacks or delusions.
This drug was very popular in the 1960s, with the hippie movement, before quickly being outlawed and banned in many countries.

It was the hallucinogenic characteristics of rye slang and LSD that interested agencies like the CIA. They were then looking for an incapacitating chemical weapon. However, everyone quickly realized that this substance is not ideal. The tests (full-scale!) were not successful and the idea was abandoned.

>> Also read: Neuroscience: LSD creates a lock in the brain

And ergot today?

It is not easy to know precisely the number of people who actually died from this disease. However, this certainly amounts to millions of deaths, with some historians estimating that ” the majority of amputees who circulated in the streets from the Middle Ages until the 18th century were undoubtedly victims of gangrene » due to ergotism.
It is the late identification of the disease, among other things, which is responsible for this high mortality and the equally large number of amputees. Thus, it was not until the Age of Enlightenment that ergot was identified and implemented.

In reality, the disease mainly affects poor populations who eat mainly cereals, with little protein. In our current societies, the disease has almost disappeared. Flour manufacturers are very careful when washing grains. Moreover, the ergot content in cereals is strictly regulated by European Regulation 2023/915. It has been further revised downwards, the quantity not having to exceed 0.2 g/kg since June 30, 2025.

>> Also read: A 60-year-old man asks ChatGPT for dietary advice and develops rare poisoning causing hallucinations and paranoia