Since agreeing to chair the NAMA Toxicology
Committee in the summer of 2003, I have scanned the over 1,700
reports of mushroom poisonings in the NAMA registry maintained
since 1984. I have fully reviewed the reports for 2001, 2002, and
2003, which total 130 human cases involving 192 people and 23 reports
of poisonings of dogs (involving 25 dogs).
Of all poisonings reported to poison and drug centers, about two
thirds involve ingestions (usually by young children) where no symptoms
are observed. Nearly every case where symptoms are observed involves
either vomiting or diarrhea, usually both.
The most striking aspect of all of the reports was how rarely a
human died from a mushroom ingestion. Even people who ate one of
the deadly Amanita species usually survived (though often with significant
liver damage). In fact, the two cases of human deaths in Canada or
the United States in the past three years where mushrooms were eaten
shortly before death of the individual were not attributed to consumption
of mushrooms, but were clearly due to other causes.
With dogs, there were eight reported deaths in the past three years.
What was striking to me was that a dog could die within hours after
ingesting a deadly Amanita.
The other surprises were that there are stinkhorns (Phallus
impudicus or similar mushrooms) that can cause contact
skin rashes just from handling them and that the juice from Omphalotus
illudins/olearius may cause a burning sensation on the skin.
Tracking down mushroom poisonings involves a lot of sleuthing and
a fair amount of guesswork. Often, no experienced mushroomer ever
sees the suspect mushroom. Even when an individual studies a collection,
it is often unclear whether or not the mushrooms examined were the
same as the mushrooms consumed. Was there just one toxic mushroom
mixed in with other edibles and no evidence remains of the toxic
species? It is particularly difficult to get the dogs to tell you
exactly what they ate or when they ate it.
On top of all of this, underlying disease may lead to lethal results
with a mushroom that is not normally deadly. Excessive consumption
of a normally edible mushroom can lead to ill effects due to the
high levels of indigestible chitin and novel amino acids and other
unusual compounds present in mushrooms. Consumption of raw mushrooms,
undercooked mushrooms or mushrooms that have been frozen raw
and then cooked can lead to adverse effects in otherwise edible species.
A surprisingly wide range of mushrooms, including morels, can cause
ill effects in some individuals if alcohol is consumed with or reasonably
soon after the meal. Also, individuals can become sensitized to a
toxin with repeated exposure; thus, after eating a mushroom several
times, additional meals of the mushroom can lead to poisoning.
Finally, dogs (and rarely cats) are attracted to mushrooms, presumably
by the sometimes fishy odor or odor of rotten meat in some species.
Pets may eat as much as a human, but with their small body mass,
they can suffer lethal effects from mushrooms that are only very
rarely, if ever, deadly with humans. also, with dogs the mushrooms
that contain a-amanitin and similar toxins can be lethal within hours
of ingestion; whereas in cases of human toxicity, onset of symptoms
is 12 hours or more, and death, if it occurs, takes a week or more.
With pets, ingestion of Amanita muscaria, Amanita
look-alikes), and probably some species of Inocybe can sometimes
lead to death, while the same species are very rarely lethal in humans
(and then only in humans with underlying infirmities).
There are a few general observations that I can now make about mushrooms
and mushroom poisonings. Other than children and dogs, people rarely,
if ever, eat small, thin-fleshed mushrooms. While many of these small
mushrooms contain muscarine and some contain a-amanitin, they simply
do not show up in the poisoning statistics (the one exception is
Lepiota josserandii, which has killed both humans and dogs).
Even though they are often large and abundant, Cortinarius species
showed up only once in all of the reports, and then it was in a mixed
ingestion of old rotten mushrooms, none of which should have been eaten
in the first place. Since a few Cortinarius species may be
deadly (with a very long onset of symptoms), I was surprised at their
nearly total absence from the reports. conversely, I was struck by
the large number of poisonings due to many different species of morels.
Some morel poisonings involved consumption of alcohol, some involved
raw or undercooked mushrooms, but some involved fully cooked, choice
morels. It appears that a large number of people are sensitive to this
mushroom. However, I was also surprised about the number of people
who ate morels raw and were not poisoned.
Nearly all of the choice edible mushrooms appeared at least once
in the poisoning lists. These reactions are attributed to food sensitivities.
Boletes, especially Leccinum species, accounted for more
than their share of poisonings by mushrooms generally considered
to be edible. Even though I have never been adversely affected by Leccinum species
and have eaten them a lot, after noting the number poisonings, the
intensity of the symptoms, and the long period of feeling poorly, I
believe my days of eating them may well be over. My colleague Marilyn
Shaw has convinced me that we are not dealing with just a food sensitivity
here. The questions include 1) are there several toxic Leccinum species,
and/or 2) are we dealing with mushrooms that contain variable levels
of toxins and so sometimes will cause poisonings and sometimes not?
These questions remain to be answered. So far, I am not aware of any
voucher specimens of specific Leccinum mushrooms that have caused a
poisoning, and getting such vouchers in the future will help answer
some of these questions.
Of the mushrooms generally considered poisonous, the one far most
often consumed is Chlorophyllum molybdites. It is large and
meaty; it resembles a generally choice edible, Lepiota
(Chlorophyllum) rachodes, it tastes good; and it grows in lawns
and parks. Chlorophyllum molybdites quickly rewards the unwary
with gastric distress, vomiting, and diarrhea lasting several hours.
Both Amanita muscaria and Amanita pantherina are
large, showy, and delicious, though poisonous mushrooms (unless cooked
by boiling them and then discarding the water — but if you
don't get rid of all the water, look out!). Though people
in Russia frequently parboil and eat Amanita muscaria, it
is not a practice I recommend. Amanita muscaria and Amanita
pantherina are frequently
eaten intentionally by people seeking to get high and are also frequently
eaten by mistake (believe it or not, often from people thinking they
had an Agaricus). The "trip" from Amanita
muscaria and Amanita
pantherina is generally not pleasant and involves hospitals more
predominately than hallucinations.
Speaking of bad trips, the poisoning case reports also contain a
steady supply of poisonings of teenagers (and occasionally old hippies)
who consume hallucinogenic mushrooms and suffer anxiety and other
ill effects from bad trips, contaminated mushrooms, and/or misidentification.
Compared to going out and randomly eating plants in the woods and
in flower beds, eating wild mushrooms is quite safe. Only about 10%
of the poisonous species are potentially deadly. Plant toxins are
far more common, more often deadly, and generally much faster in
their action. The difference is that people usually do not go around
randomly sampling plants growing in flower gardens or in the wild,
while they do eat mushrooms that they have not identified and may
not even have a clue as to how to properly identify. They also eat
mushrooms that are spoiled, where plants in a similar state of decay
would have been discarded. At the same time people tend to be more
generally terrified of eating mushrooms. Thus when the effects are
unpleasant, the consequences are often modified by feelings of panic,
especially among populations of people from Eastern Europe and Asia
where, unlike North America, deaths from mushroom poisoning are not
My Web site, www.evergree.edu/mushrooms,
which includes a section on poisonous and hallucinogenic mushrooms,
and other Web resources are sometimes used by people trying to identify
a mushroom implicated in a poisoning. I created my site hoping to
assist medical personnel in identifying mushrooms involved in a poisoning
case, and to give people some idea of what to expect in specific
poisoning cases. The problem is that doing identifications just
from a picture is a challenge, especially for someone untrained in
mycology. What we need are more people trained in mushroom identification
who are willing to help out in mushroom identification for poisoning
cases and file reports on mushroom poisonings that come to their
To aid interested mushroomers, forms and information about mushroom
toxicology can be found on the NAMA Web site, www.namyco.org.
My hope is to get more members of the mycological community involved
in identifying and reporting mushrooms involved or suspected in poisonings
so that we can have an ever better understanding of any risks associated
with mushroom consumption and so that we can better educate the general