Morchella punctipes, courtesy T. Lockwood.
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Morchella punctipes, courtesy T. Lockwood. 16 FUNGI Volume 14:2 Spring 2021
North American Mushroom
Poisonings and Adverse Reactions
to Mushrooms 2018–2020
Michael W. Beug
Toxicology Chair, North American Mycological Association
I
n his article “World Mushroom reported involve consumption of raw contain heat-labile carcinogens. However,
Production: An Overview” (FUNGI or only lightly cooked mushrooms. some toxins, like amanitins, are not
14[1]: 8–13) Dr. Britt Bunyard The culprit is lentinan, a chemical that decomposed on heating and so species
reported that there has been a 30-fold receives broad use in cancer therapy in containing amanitins (notably Amanita
increase in commercial mushroom Japan and some other Asian nations. species in the Section Phalloideae, like
production since 1978. World per capita However, about 4% of all people have Amanita phalloides and the Amanita
mushroom consumption has grown to an adverse reaction to lentinan, which bisporigera group remain toxic even after
4.7 kg/year from 1 kg/year in 1997. Over in susceptible individuals, can cause cooking).
half of all mushrooms consumed are rupture of the microcapillary blood Mushrooms may also be contaminated
cultivated edibles, 38% are medicinals, vessels. The result is a very painful rash by bacteria which would be killed on
and 8% are wild harvested. that can last for a week or more. The cooking.
I was curious about how these changes rash is known as “shiitake flagellate Pleurotus species (oyster and king
might be reflected in mushroom- dermatitis.” Lentinan is destroyed by oyster mushrooms) are the second most
poisoning data. I had not summarized heating, so cooking the mushrooms widely cultivated edible mushrooms,
the poisonings reported to NAMA prevents the painful rash. A very tiny occupying 19% of the cultivated sales
since 2017 and it was time for me to percentage of people have an adverse market. While most people tolerate
update the mushroom poisoning case reaction even to well-cooked shiitake, cooked oyster mushrooms, consumption
registry. The full update, “Summary of typically suffering diarrhea, vomiting, of raw and undercooked oyster
the Poisoning Reports in the NAMA intestinal cramps, and nausea. There mushrooms is a very significant cause
Mushroom Poisoning Case Registry: are no mushrooms, indeed no foods of of gastrointestinal upset, sometimes
2018 through 2020” was published in any kind, that do not cause problems for leading to hallucinations. On rare
McIlvainea vol. 30 (2021) and is available some sensitive individuals. Shiitake is occasions, someone will have a bad
free online at www.namyco.org. In this possibly the most widely tolerated of all reaction even to well-cooked oyster
note, I highlight findings from the full foods—if it is well cooked. mushrooms if they drink alcohol with
report. Tables I and II are reproduced Thorough cooking is important for all their meal. However, most people
from McIlvainea vol. 30. edible fungi. The exception is truffles. can eat oyster mushrooms and drink
It is noteworthy that the NAMA data The cell walls of fungi are chitin, which alcohol with no problem. One woman
is a result of voluntary reporting and is very indigestible, but is made more who consumed several raw stipes of
only captures a small fraction of the digestible on cooking. Though I have not cultivated blue oyster mushrooms
adverse events in any one year. Most seen it reported recently, consumption suffered chills, flushing, diarrhea,
adverse reactions (to any mushroom) go of raw and undercooked mushrooms intestinal cramps, sweating, muscle
unreported to NAMA. can lead to a bezoar, a serious blockage spasms, vomiting, drowsiness, weakness,
Globally, Lentinula edodes (shiitake) of the stomach or intestines due to headache, and blotchy skin on her face.
is the dominant cultivated mushroom the formation of a bolus of undigested I no longer eat any oyster mushrooms
at 22% of world cultivated mushroom material. Several edible mushrooms, because 1) there are many other species
production. Prior to 10 years ago, I had most notably morels (indeed, all that I like far better and 2) I have seen
never seen a reported adverse reaction species of edible ascomycetes, except too high a percentage of bad experiences
to shiitake in North America. Now culinary truffles), are poisonous raw, with Pleurotus species.
adverse reactions to shiitake are one of containing unknown compounds that Auricularia species (wood ears, also
the 10 most common events reported are decomposed upon heating. Other called black fungus), a flavorless jelly
to NAMA. Most of the adverse cases species, including Agaricus species, mushroom with great texture, are third
Spring 2021 FUNGI Volume 14:2 17
Flammulina velutipes, courtesy N. Craig. in annual production. I had expected poisonings reported to NAMA over or winter mushroom), at 11%, ranks them to also be prominent in the toxicity the past three years (8 cases). This is fifth in global production. I have no category, but have not had a single counting both “edible” and “poisonous” recent reports of adverse reactions report of a bad reaction for several years species! The problem is typically from the mushroom itself, which is now. They are very popular in Chinese gastrointestinal upset accompanied by prized both for its healthy properties cuisine and are used medicinally for flu-like symptoms. In some cases, there is (low cholesterol, etc.) and for a range purported antitumor, hypoglycemic, a clear allergic reaction accompanied by of purported medicinal benefits. anticoagulant, and cholesterol-lowering rash. A good way to tempt fate is to help However, contamination by Listeria properties. The anticoagulant properties yourself to some of the raw sliced button monocytogenes, found growing on are very real and lead to a poisoning mushrooms typically found in salad imported enoki mushrooms, led to 31 known as Chinese restaurant syndrome. bars. Pass on them and do the restaurant people hospitalized plus four deaths The blood-thinning properties can owner a favor and tell them not to serve in 17 states in June of 2020. When lead to excess bruising and horrendous raw or only lightly cooked mushrooms. purchasing cultivated mushrooms, I only menstrual periods. Unwary diners on From the wild, I place Agaricus species buy American. While problems with blood thinners are in danger of too much in one of two camps. The prized almond imported mushrooms are not common, blood thinning and excess bleeding. or anise-smelling species (all edible for I see such reports often enough to be Agaricus species, mainly Agaricus most people) and the ones that smell wary of imported mushrooms, even bisporus (the common button a bit like wet asphalt (poisonous for dried mushrooms. Cultivation practices mushroom, also known as baby bellas, most people). I have never tried one in North America mean that mushrooms crimini, and portobellos) occupy of the foul-smelling species, but even from North America are far less likely to fourth place in global production. Until the choice almond-smelling species be contaminated. this most recent three-year period, like Agaricus augustus will give me I have also seen a recent surge in Agaricus bisporus rarely showed up in gastrointestinal distress. One consumer reports of people becoming ill from mushroom poisoning reports. However, of a foul-smelling Agaricus species, when bags of imported dried mushrooms with the huge increase in mushroom presenting at the hospital for treatment, containing a mixture of species. If you consumption, Agaricus bisporus noted that they tasted “a bit off.” suffer gastrointestinal distress, how has climbed to number one in total Flammulina species (enoki, enokitake, are you to know which species in the 18 FUNGI Volume 14:2 Spring 2021
mixture caused your problem? When different properties than the fruitbody
purchasing dried mushrooms, stick to and both can be beneficial.
single species. You can mix your own Among the medicinal mushrooms,
later once you have safely eaten each I see the most problems with Inonotus
species separately. obliquus (chaga). Chaga forms a black
Cultivation of medicinal mushrooms canker typically on birch trees in
accounts for about 38% of global northern latitudes. I have case reports
production. I regularly consume a few of people harvesting a black growth on
species of “medicinal mushrooms.” conifers and a different black growth
My number one favorite is Hericium on cherry trees that were not chaga,
erinaceus (lion’s mane). Cultivated and both caused severe gastrointestinal
species have a great texture and a distress. Just because something is a
very nice flavor. Wild lion’s mane in polypore does not necessarily mean
my area tastes like lobster. I prefer it that it is not poisonous. Even when
to every other edible species. In Asia correctly identified, things do not
one important use is in slowing the always go well. In one case involving
progression of dementia. In vitro study unspecified preparation, an individual
evidence indicates that it has powerful suffered hepatitis and renal failure from
neurogenerative properties. Maybe it “chaga.” In a second case, consumption
will slow my own growing dementia; of “chaga” tea led to three days of
it certainly cannot hurt. It certainly is vomiting and confusion, elevated liver
delicious. Another powerful, but little enzymes, elevated serum creatinine, and
appreciated, medicinal mushroom is coagulopathy. In a third case a person
Boletus edulis. The stipes are loaded with drank “chaga” tea for two weeks and
beta glucans, which many people believe then his trunk and legs turned purple.
are very good for you. I eat as many king Another kept a container of “chaga” tea,
boletes as I can find. Just don’t mess drinking from it regularly, winding up
up and consume an East Coast look- hospitalized after the tea turned moldy.
alike, Boletus huronensis. It can cause Among other polypores, I have four
nasty and long-lasting gastrointestinal recent reports of gastrointestinal distress
distress. I consume two lion’s mane from Grifola frondosa (maitake or hen
capsules and one Trametes versicolor of the woods). For most people, this
(turkey tail) capsule every weekday. I is a prized edible. I certainly would
strongly believe in the ability of turkey not hesitate to consume it. But as
tail mushroom capsules to aid in dealing with all foods, for some it can cause
with solid cancers. However, harvesting gastrointestinal distress or worse. One
in the wild can present problems. First, case is particularly instructive. An
there are a lot of turkey tail look-alikes adult woman reported her experience
when viewed just from the top. It is the consuming this mushroom on four
combination of the appearance from the different occasions. The mushroom was
top plus the small white pores on the thoroughly cooked each time. After the
underside that is distinctive. Also, some first two meals, all was well. However,
cultivars have much higher production the third meal produced a minor
of beneficial compounds than others and stomachache. The fourth meal resulted
so with wild harvesting you never know in intestinal cramps and vomiting. Her
whether you are picking a potentially body has probably developed a sensitivity
medicinally useful mushroom or to this species and were she to continue
one with only low production of the eating maitake, each subsequent episode
chemicals of interest. Finally, make sure could be much worse.
that if you do harvest from the wild The polypore complex Laetiporus
that you harvest fresh, prime material. sulphureus, L. cincinnatus, L.
Old turkey tail mushrooms can cause conifericola, and L. gilbertsonii is
significant gastrointestinal distress. Even particularly problematic with four
with purchased “turkey tail” capsules, it recent cases in the NAMA case
is important to buy from someone who registry. A woman from Georgia
has researched many cultivars to find reported consuming a large amount
one with strong medicinal properties of boiled and then thoroughly sautéed
(based on test tube or Petri dish studies). mushrooms. She had an allergic reaction
It is also important to realize that the and broke out in hives that lasted
mushroom mycelium can have very a couple of weeks. A woman from
Spring 2021 FUNGI Volume 14:2 19
New York consumed ¾ cup of well- eating these boletes for years and then “edible” to the “poisonous” category.
cooked mushrooms. She had eaten this suddenly developing a sensitivity to Even well-cooked specimens can cause
species once before and suffered slight them, developing flu-like symptoms that sufficiently severe diarrhea, intestinal
indigestion. This time it was a full-blown can last for a week or more. For some cramps, vomiting, nausea, and weakness
allergic reaction resulting in chills, people, even the first meal is problematic. to send one to the hospital. We had four
salivation, dizziness, intestinal cramps, There are seven recent reports of adverse such reports in the database.
muscle spasms, vomiting, weakness and reactions to Leccinum species, putting Morchella species often take first place
rash. A few years ago, an Oregon woman this group second only to Agaricus for for causing the most adverse incidents
took two bites of L. conifericola and died number of reports. If you do continue over the course of a year, even beating
from anaphylactic shock. I steer clear of eating these, make doubly sure that they out the always-toxic Chlorophyllum
all Laetiporus species. are very thoroughly cooked (and even molybdites. There is no way I am going
Leccinum species were once regularly that may not be adequate). to stop eating morels. They are just too
on the menu at our home. No longer. I Sutorius (Tylopilus) eximius is another delicious. However, I do not trust other
have seen too many reports of people bolete that needs to be moved from the people to cook them thoroughly and so
Table I. Summary of Human Cases.
Toxin or Number of
Notable Observations
Poisoning Syndrome Cases
No deaths. One person survived eating ½ Amanita bisporigera and
Amatoxins 10 cases
survived without treatment.
Two young children escaped with no symptoms due to fast treatment.
Isoxazoles 13 cases One adult consumed huge quantity and was treated with atropine and
experienced respiratory failure—recovered after 8 days.
One probable anaphylactic shock. Two atypically severe cases involving
purchased Psilocybe species that were likely adulterated. One young child
Psilocybin 7 cases
promptly treated had no symptoms from P. cyanescens which can cause
death in young children.
Second ever orellanine case reported in North America.
Orellanine 1 case
Severe kidney damage.
Allenic norleucine 1 case + Violent poisoning. No mention of typical kidney damage. Always from
chlorocrotylglycine 1 possible Amanita smithiana.
Bleeding None
Cases of possible alcohol reactions due to individual sensitivity recorded
Alcohol syndrome None
under gastrointestinal cases.
Gyromitrin None
One DEATH from a Clitocybe (from 2014). One gastrointestinal
case where one Clitocybe may have been consumed. One severe
3 cases +
Muscarine gastrointestinal case where an Inocybe was consumed to get high. One
1 possible
young child case involving part of an Inocybe, prompt treatment, and no
symptoms.
Contamination by 1
Four DEATHS, 31 hospitalized in 17 states.
Listeria shipment
Many lessons here but the most important is that some people can
Gastrointestinal become sensitive to a mushroom that they have eaten for years. Repeated
130 cases
and/or shock ingestions of that species can lead to increasing severity of symptoms.
Historically has caused deaths from anaphylactic shock.
20 FUNGI Volume 14:2 Spring 2021only eat ones that are clearly fresh (not practice. Cooks have died from inhaling and ibotenic acid) was implicated
starting to rot) and that I have cooked the vapors while cooking. in 13 human cases (two Amanita
myself. In this most recent period, There were five reports of adverse multisquamosa, five Amanita muscaria,
morels tied with C. molybdites at six reactions to Hypomyces lactifluorum and six Amanita pantherinoides
incidents. Morels are clearly poisonous (lobster mushroom), though two of (=American A. pantherina) plus many
raw, but none of the six reports involved those involved mixed collections. This dog cases and one case involving three
raw mushrooms, though a couple of species has only recently started showing ducks (a first ever report involving any
cases were suspect because of light up in the NAMA case reports. In two species of bird). On the day the ducks
cooking. Symptoms generally include cases, the individual reported that they consumed A. pantherina, the ducks were
dizziness, disorientation, intestinal had previously eaten lobster mushrooms so sick that the owner thought that they
cramps, vomiting, drowsiness, sweating, for years without adverse effects. would all die. However, the next day they
and flushing. A few people cannot eat Reported effects include chills, intestinal had all fully recovered. The symptoms
morels and drink alcohol, though most cramps, sweating, vomiting, nausea, in the ducks were just what one would
people can do so without adverse effect. weakness, and headache. expect from either a human or a dog
Some people who have eaten morels Among toxic mushrooms, species case. The recovery was also typical.
without incident for years, can suddenly containing amatoxins are the most Of the human isoxazole poisonings,
develop a sensitivity to them. If that feared. Ten human case reports involved some of these involved intentional
happens and you eat morels again and suspected or confirmed amatoxin ingestions by individuals intent on
the reaction is even worse, stop eating poisoning. There were no reported getting high and who wound up in
morels. Another meal could prove life human deaths or liver transplants in the hospital for their efforts. These
threatening. This warning is true for the past three years. Many more cases species all contain muscarine as a
any edible mushroom that you become involved dogs (where the outcome is secondary toxin. Muscarine poisoning is
sensitive to. usually death). The human amatoxin counteracted with precise doses of the
Morels do not contain significant cases included two with Amanita toxin atropine. However, in dogs who
quantities of gyromitrin, if any at all. bisporigera (including one person who have ingested isoxazoles, use of atropine
Gyromitrin is found in significant survived without seeking any treatment), is contra-indicated since it exacerbates
quantity in Gyromitra esculenta, G. three or possibly four with Amanita the isoxazole poisoning and can lead to
ambigua, and G. infula as well as in phalloides (including one unsuccessful death. Atropine was also used in one
Cudonia circinans. Fortunately, we suicide attempt), and one each with human isoxazole case and appears to
have had no poisoning reports from Conocybe filaris, Lepiota lilacea, have significantly increased the severity
any of these four toxic species over the and Lepiota subincarnata and one of the poisoning.
past three years. Gyromitrin is highly apparent amatoxin poisoning due to an Several human and dog cases involved
carcinogenic and can cause severe liver unidentified species. There were no cases ingestion of Inocybe and Clitocybe
damage, even death. Thorough cooking due to Galerina autumnalis/marginata. species that are high in muscarine. These
(outside) will destroy the gyromitrin This was a first ever report for both L. species contributed to several dog deaths
and vaporize the toxic monomethyl lilacea and C. filaris. and the first ever human death (in the
hydrazine, rendering G. esculenta Inebriation and poisoning by isoxazole NAMA database) from a Clitocybe.
edible, though I do not recommend the compounds (notably muscimol Reading through the full report in
Table II. Overall Summary of Animal Cases.
Toxin or Number of Notable Observations
Poisoning Syndrome Cases
Amatoxins 15 cases Twenty DEATHS, 2 recovery (1 from Amanita phalloides, 1 from
25 dogs Lepiota subincarnata). The rest, largely unknown outcome.
Isoxazoles 11 cases Three DEATHS (all dogs). First mushroom poisoning report of any
11 dogs + kind involving ducks. Duck symptoms typical for isoxazole poisoning,
3 ducks 24 hour recovery.
Muscarine 12 cases Two DEATHS.
15 dogs
Psilocybin none Dogs are known to seek out and consume Psilocybe mushrooms.
Gyromitrin 2 cases One DEATH.
Gastrointestinal 18 cases Three DEATHS. Two DEATHS from unknown toxins in Amanita
19 dogs (Saproamanita) thiersii. One DEATH from probable Panaeolus
foenisecii.
Spring 2021 FUNGI Volume 14:2 21McIlvainea, you will note several additional
species with just one or two reports of adverse
effects. One remaining case of note was a very
serious poisoning by Cortinarius rubellus, one
of two North American Cortinarius species
known to contain orellanine, a chemical with
a very long lag time between ingestion and
symptoms (days to weeks). Orellanine leads
to loss of kidney function and can result in
death (several cases in Europe) or the need for
a kidney transplant. There has only been one
other recorded orellanine poisoning case in
North America and that was a Michigan case
due to C. orellanosus. While C. rubellus is a
conifer associate found in sphagnum bogs,
C. orellanosus is associated with hardwoods.
Both are mistaken for chanterelles, though the
gills of the Cortinarius species are distinctly
different from the blunt ridges of a chanterelle.
Consumption of Psilocybe species in the
right set and setting, and under proper
guidance, can have exceptional medical
benefits. At numerous psychedelic mushroom
conferences where Psilocybe mushrooms
were consumed, I have never observed a “bad
trip” (and yes, on all but one occasion, I was
simply an observer). However, misuse can
have significant adverse consequences. One
“bemushroomed” individual consumed an
assortment of small brown Entoloma species
and was severely poisoned. In a second
incident, someone experienced temporary
paralysis. Though rarely reported to NAMA,
poison centers regularly deal with “bad trips.”
In two British Columbia cases and one other
Canadian case, two involving purchased
Psilocybe cubensis and one involving purchased
Psilocybe cyanescens, the symptoms lead me
to suspect that the purchased mushrooms
had been adulterated with additional, more
dangerous, psychoactive substances.
Chlorophyllum molybdites normally leads
the pack for all mushroom poisonings. I
had four reports of people who consumed
this mushroom raw. It caused very violent
poisoning including bloody vomit and
bloody diarrhea. Cooking does not render C.
molybdites edible.
Until creating this report, I had never
heard of a human death due to muscarine.
However, an old report from 2014 was turned
in reporting a human death from a Clitocybe
species. In one other case, while seeking
mushrooms to get him high, an adult suffered
muscarine poisoning after consuming Inocybe
sindonia collected on a roadside (collecting in
such a contaminated environment is a problem
on its own). The hospital bill probably proved
quite steep, but he did survive.
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