Mushroom poisoning, also known as mycetism, refers to deleterious effects from ingestion of toxic substances present in a mushroom. These symptoms can vary from slight gastrointestinal discomfort to death. The toxins present are secondary metabolites produced in specific biochemical pathways in the fungal cells. Mushroom poisoning is usually the result of ingestion of wild mushrooms after misidentification of a toxic mushroom as an edible species. The most common reason for this misidentification is close resemblance in terms of colour and general morphology of the toxic mushrooms species with edible species. Even very experienced wild mushroom gatherers are sometimes poisoned by eating toxic species, despite being well aware of the risks.
To prevent mushroom poisoning, mushroom gatherers need to be very intimately familiar with the mushrooms they intend to collect, including knowledge of the toxic species that look similar to these edible species. Other considerations regard methods of preparation and toxicity of some fungal species that appears to vary with geographic location, raising the potential of mushroom poisoning due to local toxicity of a correctly identified species.
There are many folk traditions concerning the defining features of poisonous mushrooms.
Unfortunately there are no general identifiers for poisonous mushrooms, and so such traditions are unreliable guides. Use of folk traditions to try to identify edible mushrooms are a frequent cause of mushroom poisoning.
Examples of such erroneous and highly misleading folklore "rules" include:
- "Poisonous mushrooms are brightly colored." While the toxic/hallucinogenic fly agaric is usually bright red or yellow, the deadly destroying angel is an unremarkable white, and the deadly Galerinas are brown. Some choice edible species (chanterelles, Amanita caesarea, Laetiporus sulphureus, etc.) are brightly colored, while most poisonous species are brown or white.
- "Insects/animals will avoid toxic mushrooms." Fungi that are harmless to invertebrates can still be toxic to humans; the death cap, for instance, is often infested by insect larvae. Also, animals don't always know to avoid poisonous species.
- "Poisonous mushrooms blacken silver." None of the known mushroom toxins have a reaction with silver.
- "Poisonous mushrooms taste bad." People who have eaten the deadly Amanitas reported that they tasted quite good.
- "All mushrooms are safe if cooked/parboiled/dried/pickled/etc." While it is true that some otherwise inedible species can be rendered safe by special preparation, many toxic species cannot be prepared in such a way as to make them edible. Many fungal toxins are not particularly sensitive to heat and so are not broken down during cooking.
- "Poisonous mushrooms will turn rice red when boiled". A number of Laotian refugees were hospitalized after eating mushrooms (probably toxic Russula species) deemed safe by this folklore rule.
Causes of mushroom poisoning
Of the many thousands of mushroom species in the world, only 32 have been associated with fatalities, and an additional 52 have been identified as containing significant toxins. By far the majority of mushroom poisonings are not fatal, but the majority of fatal poisonings are attributable to the Amanita phalloides
A majority of these cases are due to "mistaken identity." One way this can happen is that the victim attempts to apply folk knowledge from one area to another geographic area. This is a common occurrence with A. phalloides in particular, due to its resemblance to the Asian "paddy-straw" mushroom, Volvariella volvacea. Both are light-colored and covered with a universal veil when young.
Amanitas can be mistaken for other species, as well, particularly when immature. On at least one occasion they have been mistaken for Coprinus comatus. In this case the victim had some experience in identifying mushrooms, but did not take the time to correctly identify these particular mushrooms until after he began to experience symptoms of mushroom poisoning.
The author of "Mushrooms Demystified", David Arora cautions puffball-hunters to beware of Amanita "eggs", which are Amanitas still entirely encased in their universal veil. Amanitas at this stage are difficult to distinguish from puffballs.
A majority of mushroom poisonings in general are the result of small children, especially toddlers in the "grazing" stage, ingesting mushrooms found in the lawn. While this can happen with any mushroom, Chlorophyllum molybdites is often implicated due to its preference of growing in lawns. C. molybdites causes severe gastrointestinal upset but is not considered deadly poisonous.
A few poisonings are the result of misidentification while attempting to collect hallucinogenic mushrooms for recreational use. In 1981, one fatality and two hospitalizations occurred following consumption of Galerina autumnalis, mistaken for a Psilocybe species. Galerina and Psilocybe species are both small, brown, and sticky, and can be found growing together. However, Galerina contains amatoxins, the same poison found in the deadly Amanita species. Another case reports kidney failure following ingestion of Cortinarius orellanus, a mushroom containing orellanine.
Naturally, accidental ingestion of hallucinogenic species also occurs, but is rarely harmful. Cases of serious toxicity have been reported in small children. Amanita pantherina, while it contains the same hallucinogens as Amanita muscaria (e.g., ibotenic acid and muscimol), has been more commonly associated with severe gastrointestinal upset than its better-known counterpart.
Although usually not fatal, Omphalotus olearius, the "Jack-o-lantern mushroom," is another cause of sometimes significant toxicity. It is sometimes mistaken for a chanterelle. Both are bright orange and fruit at the same time of year, although O. olearius grows on wood and has true gills rather than the veins of a Cantharellus. It containes muscarine, which causes vomiting, diarrhea, salivation, perspiration, and tears. In high doses it can cause respiratory failure. The same toxin occurs in Clitocybe dealbata, which is occasionally mistaken for an oyster mushroom or other edible species.
Toxicities can also occur with collection of morels. Even true morels, if eaten raw, will cause gastrointestinal upset. Therefore morels should always be thoroughly cooked before eating. Verpa bohemica, although referred to as "thimble morels" or "early morels" by some, have caused toxic effects in some individuals. "False morels" or Gyromitra spp., are deadly poisonous if eaten raw. They contain a toxin called gyromitrin, which can cause neurotoxicity, gastrointestinal toxicity, and destruction of the blood cells. The Finns consume the mushroom after parboiling, but it is not known if this renders the mushroom entirely safe, resulting in its being called the "fugu of the Finnish cuisine."
A more unusual toxin is coprine, a disulfiram-like compound which is harmless unless ingested within a few days of ingesting alcohol. It inhibits aldehyde dehydrogenase, an enzyme required for breaking down alcohol. Thus the symptoms of toxicity are similar to being both drunk and "hung over" -- flushing, headache, nausea, palpitations, and in severe cases, trouble breathing. Coprinus species, including Coprinopsis atramentaria, contain coprine. Notably, Coprinus comatus does not, but it is best to avoid mixing alcohol with other members of this genus.
Recently, poisonings have been associated with Amanita smithii. These poisonings may be due to orellanine, but the onset of symptoms occurs in 4 to 11 hours, which is much quicker than the 3 to 20 days normally associated with orellanine.
In some cases, toxicity can occur even with mushrooms that are widely considered edible.
Paxillus involutus is also indigestible when raw, but is eaten in Europe after pickling or parboiling. However, after the death of the German mycologist Dr Julius Schäffer, it was discovered that the mushroom contains a toxin which can stimulate the immune system to attack its own red blood cells. This reaction is rare, but can occur even after safely eating the mushroom for many years. Similarly, Tricholoma equestre was widely considered edible and good, until it was connected with rare cases of rhabdomyolysis.
In the fall of 2004, thirteen deaths were associated with consumption of Pleurocybella porrigens or "angel's wings." These mushrooms are generally considered edible. All the victims died of an acute brain disorder, and all had pre-existing kidney disease. The exact cause of the toxicity was not known at this time.
Cases of idiosyncratic or "unusual" reactions to fungi can also occur. Some are probably due to allergy, others to some other kind of sensitivity. It is not uncommon for an individual person to experience gastrointestinal upset associated with one particular mushroom species or genus. Eating small portions when trying a new mushroom may be used as a precaution to identify individual problems with the new species.
Toxins and their symptoms
Poisonous mushrooms contain a variety of different toxins that can differ markedly in toxicity. Symptoms of mushroom poisoning may vary from gastric upset to life-threatening organ failure resulting in death. Serious symptoms do not always occur immediately after eating; often not until the toxin attacks the kidney or liver, sometimes days or weeks later.
The most common consequence of mushroom poisoning is simply gastric upset. Most "poisonous" mushrooms contain gastrointestinal irritants which cause vomiting and diarrhea (sometimes requiring hospitalization), but no long-term damage. However, there are a number of recognized mushroom toxins with specific, and sometimes deadly, effects:
- Alpha-amanitin (deadly: causes liver damage 1-3 days after ingestion) – principal toxin in genus Amanita.
- Phallotoxin (causes gastrointestinal upset) – also found in poisonous Amanitas
- Orellanine (deadly: causes kidney failure 3 weeks after ingestion) – principal toxin in genus Cortinarius.
- Muscarine (sometimes deadly: can cause respiratory failure) – found in genus Omphalotus.
- Gyromitrin (deadly: causes neurotoxicity, gastrointestinal upset, and destruction of blood cells) – principal toxin in genus Gyromitra.
- Coprine (causes illness when consumed with alcohol) – principal toxin in genus Coprinus.
- Ibotenic acid and muscimol (hallucinogenic) – principal toxin in A. muscaria, A. pantherina, and A. gemmata.
- Psilocybin and psilocin (hallucinogenic) – principal toxin in genus Psilocybe.
- Arabitol (causes gastrointestinal irritation in some people).
- Bolesatine a toxin found in Boletus satanas
Symptoms of mushroom poisoning vary depending on the toxins involved.
- Alpha-amanitin: For 6-12 hours, there are no symptoms. This is followed by a period of gastrointestinal upset (vomiting and profuse, watery diarrhea). This stage is caused primarily by the phallotoxins and typically lasts 24 hours. At the end of this second stage is when severe liver damage begins. The damage may continue for another 2-3 days. Kidney damage can also occur. Some patients will require a liver transplant. Amatoxins are found in some mushrooms in the genus Amanita, but are also found in some species of Galerina and Lepiota. Overall, mortality is between 10 and 15 percent. Recently, Silybum marianum or blessed milk thistle has been shown to protect the liver from amanita toxins and promote regrowth of damaged cells , including a study in which 60 patients exposed to death cap poison were given 20 mg/kg of milk thistle seeds per day within 48 hours of consuming the deadly mushrooms. None of the patients died.
- Orellanine: This toxin causes no symptoms for 3-20 days after ingestion. Typically around day 11, the process of kidney failure begins, and is usually symptomatic by day 20. These symptoms can include pain in the area of the kidneys, thirst, vomiting, headache, and fatigue. A few species in the very large genus Cortinarius contain this toxin. People who have eaten mushrooms containing orellanine may experience early symptoms as well, because the mushrooms often contain other toxins in addition to orellanine. A related toxin that causes similar symptoms but within 3-6 days has been isolated from Amanita smithiana and some other related toxic Amanitas.
- Muscarine: Muscarine stimulates the muscarinic receptors of the nerves and muscles. Symptoms include sweating, salivation, tears, blurred vision, palpitations, and, in high doses, respiratory failure. Muscarine is found in mushrooms of the genus Omphalotus, notably the Jack 'o lantern mushrooms. It is also found in A. muscaria, although it is now known that the main effect of this mushroom is caused by ibotenic acid. Muscarine can also be found in some Inocybe species and Clitocybe species, particularly Clitocybe dealbata, and some red-pored Boletes.
- Gyromitrin: Stomach acids convert gyromitrin to monomethylhydrazine (MMH), a compound employed in rocket fuel. It affects multiple body systems. It blocks the important neurotransmitter GABA, leading to stupor, delirium, muscle cramps, loss of coordination, tremors, and/or seizures. It causes severe gastrointestinal irritation, leading to vomiting and diarrhea. In some cases, liver failure has been reported. It can also cause red blood cells to break down, leading to jaundice, kidney failure, and signs of anemia. It is found in mushrooms of the genus Gyromitra. A gyromitrin-like compound has also been identified in mushrooms of the genus Verpa.
- Coprine: Coprine is metabolized to a chemical that resembles disulfiram. It inhibits aldehyde dehydrogenase (ALDH), which generally causes no harm, unless the person has alcohol in their bloodstream while ALDH is inhibited. This can happen if alcohol is ingested shortly before or up to a few days after eating the mushrooms. In that case the alcohol cannot be completely metabolized, and the person will experience flushed skin, vomiting, headache, dizziness, weakness, apprehension, confusion, palpitations, and sometimes trouble breathing. Coprine is found mainly in mushrooms of the genus Coprinus, although similar effects have been noted after ingestion of Clitocybe clavipes.
- Ibotenic acid: This organic acid is metabolized to muscimol. The effects of muscimol vary, but nausea and vomiting are common. Confusion, euphoria, or sleepiness are possible. Loss of muscular coordination, sweating, and chills are likely. Some people experience visual distortions, a feeling of strength, or delusions. Symptoms normally appear after 30 minutes to 2 hours and last for several hours. A. muscaria, the "Alice in Wonderland" mushroom, is known for the toxic/hallucinogenic properties caused by ibotenic acid, but A. pantherina and A. gemmata also contain the same compound. While normally self-limiting, fatalities have been associated with A. pantherina, and consumption of a large number of any of these mushrooms is likely to be dangerous.
- Psilocybin: This compound is converted into psilocin when ingested. Symptoms begin shortly after ingestion. The effects can include euphoria, visual and religious hallucinations, and heightened perception. However, some persons experience fear, agitation, confusion, and schizophrenialike symptoms. All symptoms generally pass after several hours. Some (though not all) members of the genus Psilocybe contain psilocybin, as do some Panaeolus, Copelandia, Conocybe, Gymnopilus, and others. Some of these mushrooms also contain baeocystin, which has effects similar to psilocin.
- Arabitol: A sugar alcohol, similar to mannitol, which causes no harm in most people but causes gastrointestinal irritation in some. It is found in small amounts in oyster mushrooms, and considerable amounts in Suillus species and Hygrophoropsis aurantiaca (the "false chanterelle").
Some mushrooms contain less toxic compounds and, therefore, are not severely poisonous. Poisonings by these mushrooms may respond well to treatment. However, certain types of mushrooms, such as the Amanitas, contain very potent toxins and are very poisonous; so even if symptoms are treated promptly mortality is high. With some toxins, death can occur in a week or a few days. Although a liver or kidney transplant may save some patients with complete organ failure, in many cases there are no organs available. Patients who are hospitalized and given aggressive support therapy almost immediately after ingestion of amanitin-containing mushrooms have a mortality rate of only 10%, whereas those admitted 60 or more hours after ingestion have a 50-90% mortality rate.
Three of the most lethal mushrooms belong to the genus Amanita: the death cap (A. phalloides) and destroying angels (A. virosa, and A. bisporiga); the fool's mushroom (A. verna) and two are from the genus Cortinarius: the deadly webcap (C. rubellus), and the fool's webcap (C. orellanus). Several species of Galerina, Lepiota, and Conocybe also contain lethal amounts of amatoxins. Deadly species are listed in the List of deadly fungi.
The following species may cause great discomfort, sometimes requiring hospitalization, but are not considered deadly.
- Amanita muscaria (fly agaric) – known for its use as an entheogen, and it is now known that the toxins convert to psychoactives upon drying.
- Amanita muscaria var. regalis – symptoms generally mild.
- Amanita pantherina (panther mushroom) – contains similar toxins as A. muscaria, but is associated with more fatalities than A. muscaria.
- Chlorophyllum molybdites (greengills) – causes intense gastrointestinal upset.
- Entoloma (pinkgills) – some species are highly poisonous, such as livid entoloma (Entoloma sinuatum), Entoloma rhodopolium, and Entoloma nidorosum. Symptoms of intense gastrointestinal upset appear after 20 minutes to 4 hours, caused by an unidentified gastrointestinal irritant.
- Many Inocybe species such as Inocybe fastigiata and Inocybe geophylla contain muscarine, while Inocybe erubescens is the only one known to have caused death.
- Some white Clitocybe species, including C. rivulosa and C. dealbata – contain muscarine.
- Tricholoma pardinum, Tricholoma tigrinum (Tiger Tricholoma ) – gastrointestinal upset due to an unidentified toxin, begins in 15 minutes to 2 hours and lasts 4 to 6 days.
- Tricholoma equestre Man-on-horseback – until recently thought edible and good, can lead to rhabdomyolysis after repeated consumption.
- Hypholoma fasciculare/Naematoloma fasciculare (Sulfur tuft) – usually causes gastrointestinal upset but the toxins fasciculol E and F could lead to paralysis and death
- Paxillus involutus (Brown roll-rim) – once thought edible, but now found to destroy red blood cells with regular or long-term consumption.
- Boletus satanas (Devil's bolete), Boletus luridus, Boletus legaliae, Boletus piperatus, Boletus erythropus, Boletus pulcherrimus – gastrointestinal irritation. Of these, only B. pulcherrimus has been implicated in a death. Many books list B. erythropus as edible, but Arora lists it as "to be avoided."
- Hebeloma crustuliniforme (known as Poison pie or Fairy cakes) – causes gastrointestinal symptoms such as nausea and vomiting.
- Russula emetica (the Sickener) – as its name implies, causes rapid vomiting. Other Russulas with a peppery taste (Russula silvicola, Russula mairei) will likely do the same.
- Agaricus hondensis, Agaricus californicus, Agaricus praeclaresquamosus, Agaricus xanthodermus – cause vomiting and diarrhea in most people, although some people seem to be immune.
- Lactarius piperatus, Lactarius torminosus, Lactarius rufus – these and other peppery-tasting Lactarius are pickled and eaten in Scandinavia, but are indigestible or poisonous unless correctly prepared.
- Lactarius vinaceorufescens, Lactarius uvidus – reportedly poisonous. Arora reports that all yellow- or purple-staining Lactarius are "best avoided."
- Ramaria gelatinosa – causes indigestion in many people, although some seem immune.
- Gomphus floccosus (the scaly chanterelle) – causes gastric upset in many people, although some eat it without problems. G. floccosus is related to the chanterelle and sometimes confused with it.
Other causes of poisoning
Mushrooms may be rendered poisonous by insecticides or herbicides sprayed on lawns or reserves. At least one author recommends never picking them in non-natural landscapes for this reason.
Also, mushrooms are sometimes contaminated by concentrating pollutants, such as heavy metals or radioactive material (see Chernobyl disaster effects).
Rotten mushrooms may cause food poisoning. Mushrooms which are mushy, bad-smelling, or moldy (even of a choice edible species) may be toxic due to bacterial decay or mold.
Many mushrooms are high in fiber. Excessive consumption of mushrooms may lead to indigestion, which may be diagnosed as mushroom "poisoning."