Mushroom Toxicity

By John Stuart, WPMC Past-President

Mushrooming is a fascinating hobby with many advantages. It gets us outdoors, there are more species than we can possibly identify, and they are amazing in their delicacy, beauty, variations in size, shape, color, smells, and tastes. Hunting fungi can be a lifelong experience that brings surprises with every foray. Unfortunately, eating the wrong mushroom can also kill you. Thankfully, fatalities from mushroom poisoning are quite rare.

In a mushroom poisoning emergency contact your nearest poison control center in the US or Canada, emergency room, or your physician.
US Poison US Poison control: 1-800-222-1222

Click here to contact one of NAMA’s volunteer identification consultants.
Amatoxin hot line (for silibinin , Legalon-SIL): 866-520-4412

The perception of dying from eating wild mushrooms is still widely held in North America but, in reality, deaths from toxic fungi average under five per year. During the period 2001 to 2012 there were 83,140 calls to poison control centers concerning possible mushroom poisoning.  The majority had mild symptoms and resolved without treatment or hospital visits, most involved children (77%), 5% required an emergency room evaluation, fewer than 1% were hospitalized, and there were 45 deaths (0.05%) over this 11-year period. Despite children accounting for a large proportion of reported mushroom ingestion pediatric fatalities are very rare, probably because of the small portions ingested and minimal toxicity of the mushrooms involved. Another study looked at 1,200 serious bona fide mushroom poisonings and found 50% were related to hallucinogens with no fatalities and the other 50% resulted in four deaths. The offending mushroom was usually identified only 5% to 10% of the time.

Estimates vary but, of the 10,000 or so recognized species in North America, 50 to 100 are potentially lethal. Many more can cause problems under the right circumstances. Even significant amounts of the common button mushroom can cause stomach upset when eaten raw. There is no easy method or formula to determine whether a mushroom is toxic or not. Tales such as “boiling with a silver spoon, safe if growing on wood, OK if you can peel the cap, if bugs and animals can eat it, so can I” are absolutely not true and hold no validity. Even ingesting a small amount of a toxic mushroom may cause death. Cooking, salting, or drying does not inactivate many mushroom toxins, and even fumes from cooking certain species can cause poisoning. To repeat, there are no general rules for determining if a mushroom is toxic or not.

There have been 14 distinctive categories of mushroom poisoning found worldwide and 10 distinctive patterns observed in North America, based on the toxin and clinical presentation. Each group exerts its toxic effects by a different mechanism, and certain toxins have a predilection for certain organ systems.

Major Mushroom Poisoning Syndrome Initial symptons Locally Found Species Common Name
Gastrointestinal irritants Nausea, vomiting, cramps, and diarrhea within 20 minutes to four hours after ingestion. Agaricus xanthodermus Yellow-foot agaricus
Chlorophyllum molybdites Green-spored parasol
Hebeloma crustuliniforme Poison pie
Omphalotus illudens Jack o ‘Lantern
Russula emetica Emetic Russula
Scleroderma citrinum Poison pigskin puffball
Ramaria formosa Yellow-tipped coral
Naematoloma fasciculare Sulfur tuft
Muscarine Sweating, salivation, tearing, slow heart rate, low blood pressure, blurry vision, irregular pulse, and difficulty breathing Clitocybe dealbata Sweating mushroom
Omphalotus illudens Jack o ‘Lantern
Inocybe sp.
Isoxazole derivatives Nausea and vomiting Amanita muscaria Fly agaric
Feeling drunk, drowsiness, apparent coma (muscimol) Amanita pantherina Panther cap
Or hyperactivity, myotonic jerks, convulsions, delusions, and hallucinations (ibotenic acid) Amanita gemmata Gemmed amanita
Amatoxins Severe vomiting, bloody diarrhea, and abdominal cramps with relapse 3 to 5 days after the ingestion Amanita phalloides Death cap
Amanita bisporigera Destroying angel
Galerina marginata Deadly galerina
Gyromitrin (MMH) Headache, gastrointestinal discomfort, Gyromitra esculenta False morel
Orellanine

 

Nausea, vomiting, lethargy, anorexia, frequent urination, burning thirst, headache, feeling of coldness and shivering (three days to three weeks after ingestion) Cortinarius gentilis Deadly cort
Psilocybin & other indole derivatives Heightened color perception, emotional effects ranging from ecstasy to anxiety, and sometimes hallucinations or delusions Psilocybe sp. Psilocybe caerulipes
Psilocybe ovoideocystidiata
Panaeolus sp.
Coprine & other alcohol-induced syndromes Increased heart rate, palpitations, nausea, tingling, flushing, and headache Coprinopsis atramentaria Alcohol Inky
Clitocybe clavipes Club-footed Clitocybe
Miscellaneous & Unknown:
Rhabdsomyolysis syndrome Cardiac and respiratory complications Tricholoma equestre in France Canary trich
Erythromelalgia syndrome Painful flushing of the hands, feet and nose Hygrophoropsis aurantiaca False chanterelle
Clitocybe gibba Funnel clitocybe
Rash Rash similar to poison ivy in sensitive individuals Suillus americanus Slippery Jack
Immunohemolytic anemia Gastrointestinal symptoms within three hours of ingestion Paxillus involutus Poison pax
Cyanide Marasmius oreades (if eaten raw) Fairy ring mushroom
Other Various Little Brown Mushrooms (LBM’s)

The syndromes are:

  1. Gastrointestinal irritants
  2. Muscarine
  3. Isoxazole derivatives (muscimol, ibotinic acid, and relatives)
  4. Amatoxins (cyclopeptides)
  5. Gyromitrin (MMH)
  6. Orellanine (delayed kidney damage)
  7. Psilocybin, psilocin and other indole derivatives
  8. Prompt kidney damage
  9. Coprine and other alcohol induced syndromes
  10. Miscellaneous and unknown toxins

This may be an oversimplification, as mushrooms have evolved and survived over hundreds of millions of years and have become experts in chemical warfare. Their toxic effects may be the result of not one, but many compounds they can produce, acting in concert.


Gastrointestinal irritants
are the most common form of mushroom poisoning, usually presenting symptoms of nausea, vomiting, cramps, and diarrhea within 20 minutes to four hours after ingestion. Most usually resolve within 24 hours and the prognosis is good. The most common complication is dehydration from vomiting and diarrhea, and it can be a very unpleasant experience. Chlorophyllum molybdites (green-spored parasol) and Omphalotus illudens (jack-o-lantern mushroom) are notable offenders.  Mushrooms can cause gastrointestinal problems when not properly cooked.  This includes Armillaria mellea (honey mushrooms) and even the excellent edible morels. Symptoms that begin at longer than six hours after ingestion raise the possibility of more serious toxicity from amatoxins or orellanine.


Muscarine
symptoms usually have a very quick onset, within 15 to 30 minutes after ingestion, and include sweating, salivation, tearing, slow heart rate, low blood pressure, blurry vision, irregular pulse, and difficulty breathing. Recovery usually occurs within 24 hours, but severe cases may result in death due to respiratory failure. Caused by Inocybe, Clitocybe, Omphalotus, and Entoloma species, this is the only syndrome that has a specific antidote, atropine that is administered intravenously.  Amanita muscaria (fly agaric), despite its name, produces barely detectable amounts of muscarine.


Isoxazole derivatives
(ibotenic acid and muscimol) symptoms appear fairly quickly, within 30 minutes to 2 hours after ingestion and may include nausea and vomiting but affect mainly the central nervous system. Ibotenic acid is structurally similar to glutamic acid (glutamate) which is the most abundant excitatory neurotransmitter in vertebrates. It affects perception and control – visual, spatial, and auditory distortions, hyperactivity, myotonic jerks, convulsions, and retrograde amnesia. Muscimol, a decarboxylation product of ibotenic acid, is a structural analog of gamma-aminobutyric acid (GABA) which is a major inhibitory neurotransmitter. It activates selective GABA receptors causing incoordination, feeling drunk, dizziness, and drowsiness simulating coma that can last 24 hours.  Despite these frightening conditions there have been no reliably documented deaths from these toxins and full recovery ensues with time. In humans most of the ibotenic acid ingested is secreted unchanged in urine with only a fraction being metabolized to the 5-10 times more potent muscimol. Amanita muscaria (fly agaric), Amanita pantherina (panther cap), and Amanita gemmata (gemmed Amanita) have been causative agents.


Amatoxins
(amanitins) are a group of bicyclic polypeptides which damage tissue by inhibiting RNA synthesis within cells. They cause 95% of fatalities from mushroom poisoning worldwide and in North America cause several deaths every year. Most of the fatalities are due to Amanita phalloides (death cap) which is thought to produce the highest levels of amatoxin and is widely encountered. One cap can contain 50 mg and a lethal dose is 6-7 mg. It would take 15-20 Galerina marginata (deadly galerina) caps to get an equivalent amount. The amatoxins are heat stable and not inactivated by cooking. They appear to have developed independently in multiple mushrooms not related to amanitas. Symptoms have a delayed onset: The first stage is a latency period of 6 to 24 hours when damage is being done to kidneys and liver with no symptoms; the second stage is a period of about 24 hours of severe vomiting, bloody diarrhea, and abdominal cramps; the third stage may be a period of apparent false recovery; followed by the fourth stage relapse 3 to 5 days after the ingestion, when multi-organ  (especially kidney and liver) failure and bleeding due to destruction of clotting factors occur and can lead to death. Death rates as high as 50% have now been brought down to less than 10% with aggressive supportive treatment, use of IV silibinin and liver transplant.Amanita phalloides (death cap), Amanita bisporigera (destroying angel), Galerina marginata (deadly galerina) and Lepiota species are some of the causative agents.


Gyromitrin
is hydrolyzed to monomethylhydrazine (MMH), a colorless, volatile, highly toxic carcinogenic compound that is used as rocket fuel. Symptoms appear within two to 24 hours and include headache, gastrointestinal discomfort, and in severe cases liver, kidney, and red blood cell damage leading to death–in some reports as high as 50%. It interferes with Vitamin B6. It is not clear why some people can eat mushrooms suspected of having the toxin and have no ill effects while others, even cooks who just inhale the vapors, can become deathly sick. There may be a gradual buildup of susceptibility that makes the dividing line between a safe and lethal dose slim. Treatment is similar to the amatoxins. Causative agents are in the Gyromitra group, the “false morels”, but the amount of MMH can vary from one mushroom to the next, making it difficult to determine which ones will cause trouble.


Orellanine 
is another very serious toxin causing delayed kidney damage. Onset of symptoms can occur from three days to three weeks after ingestion and include nausea, vomiting, lethargy, anorexia, frequent urination, burning thirst, headache, feeling of coldness and shivering, and evidence of progressive kidney damage. The mechanism of action is not well understood, and there is no specific treatment. Kidney transplants have been done to those who do not respond to supportive therapy. It has rarely been reported in North America. Members of the Cortinarius genus have been incriminated.


Psilocybin, psilocin and other indole derivatives
are well known as hallucinogens affecting the seratonergic system in the brain. Onset of symptoms usually begins within an hour of ingestion and lasts up to 4 to 8 hours. Effects are primarily psychological or perceptual, including heightened color perception, emotional effects ranging from ecstasy to anxiety, and sometimes hallucinations or delusions. Treatment involves mainly observation and assurance that the effects are temporary.  In rare instances severe reactions, seizures, high fever, and death have been reported. There have been efforts to incorporate them back into mainstream medical research as treatment for addiction and anxiety with some encouraging results. The mushrooms involved include about 20 species of Psilocybe and at least three Gymnopilus species, with trace amounts in others.

Prompt kidney damage due to an unknown toxin, possibly allenic norleucine or the compound chlorocrotylglycine, has caused numerous poisonings in the Pacific Northwest due to Amanita smithiana (Smith’s Amanita) that is mistaken for the popular Tricholoma magnivelare (Matsutake). These mushrooms are not found in our area.


Coprine
is a toxin known to produce symptoms of increased heart rate, palpitations, nausea, tingling, flushing, and headache that is precipitated by alcohol consumption occurring a few minutes to two hours or rarely as long as five days after ingesting the offending mushroom. Coprine generates a metabolite that inhibits acetaldehyde dehydrogenase. It is called a disulfiram-like reaction because it is similar to the effects of the drug Antabuse used for the treatment of alcoholism.  Coprinopsis atramentaria (alcohol inky)  is the main culprit.  There are other reported alcohol-induced syndromes not caused by coprine that cause gastrointestinal distress that may have a delay of up to five hours after alcohol ingestion. Coprinus comatus (shaggy mane), Clitocybe clavipes (club-footed Clitocybe), Pholiota squarrosa (scaly Pholiota), Pleurotus ostreatus (oyster mushroom), and morels have been incriminated. The cause of this association, if real and not just coincidence, is unknown.

Miscellaneous toxico-syndromes have been reported. Bolesatine produced by some boletes e.g. Boletus satanas (devil’s bolete), is a glycoprotein that inhibits protein synthesis at the ribosome.  Hematolysins that affect red blood cells include phallolysin by Amanita phalloides, rubescelysin by Amanita rubescens (blusher), and ostreolysin by Pleurotus ostreatus. These hemolysins have not caused major problems as they are not heat stable and are quickly degradable in moderate acidic conditions. Cardio toxins include flammutoxin by Flammulina velutipes (velvet foot), and volvatoxin by Volvariella volvacae (straw mushroom). Tricholoma equestre (canary trich) has been mentioned as a possible cause of muscle breakdown, rhabdomyolysis associated with cardiac and respiratory complications, leading to death in an outbreak in France. Erythromelalgia syndrome involving maldistribution of blood flow, resulting in painful flushing of the hands, feet and nose has been reported one week after ingesting certain Clitocybe species in Europe and Asia. It is thought to be caused by acromelic acid and can last for months. Hapalopilus nidulans (tender nesting polypore) and Pleurocybella porrigens (angel’s wings) have been reported to cause encephalopathy and kidney damage, possibly caused by polyporic acid. Simply handling certain mushrooms, most notably Suillus americanus (slippery jack), can cause a rash similar to poison ivy in sensitive individuals, and dermatitis has been reported after consuming raw or undercooked Lentinula edodes (shiitake), believed to be caused by the polysaccharide lentinan. Laetiporus sulpherous (chicken of the woods) was reported to cause hallucinations, nausea, vomiting and ataxia when eaten raw by a child. Lycoperdon-associated pneumonitis is thought to be an immune reaction causing the broncheoalveolar allergic syndrome seen after inhaling spores of some puffball species. An immune-hemolytic syndrome may occur after ingestion of Paxillus involutus (poison pax), presenting with gastrointestinal symptoms within three hours of ingestion, followed by an acute hemolytic anemia with hemoglobinuria and renal failure.

This is not a complete list of toxins and syndromes from poisoning. There are many others that are not known. It is not intended for medical advice.  It does give you a starting point for thinking about what things to avoid. Some people can have adverse idiosyncratic reactions to “harmless” mushrooms and some have adverse reactions to species that previously gave no trouble. One person may be poisoned by a mushroom that has no effect on another. There is also the chance of psychosomatic symptoms. Mushrooms are unpredictable. Some species are poisonous only when eaten raw, or during certain stages of maturing or season or in a particular geographic area or environment.

No doubt mushroom toxicity is an important concern when eating wild mushrooms. But there are some basic rules to follow. Since most of the fatalities occur in the amatoxin group, know how to identify them well.

  • Avoid eating Amanita
  • Don’t eat any little brown mushrooms (LBM’s).
  • Don’t eat any mushrooms that look spoiled or rotten.
  • The first time eating a new species take only a small test amount with no alcohol.
  • Avoid eating raw mushrooms.
  • Watch for possible contamination of mushrooms from environmental pesticides or herbicides.

There are certainly pitfalls, but by following common sense rules like “when in doubt, throw it out”, by educating ourselves regarding the major species offenders, and by ingesting in moderation only those mushrooms we have repeatedly identified with certainty, we should be able to stay away from any major troubles.

First published February 2018.