Mushroom Poisoning - Causes of Mushroom Poisoning

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 mushroom.

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 geographic area to another. 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 (obviously limited) 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 initially. Foragers are encouraged to always cut the fruiting bodies of suspected puffballs in half, as this will reveal the outline of a developing amanita should it be present within the structure.

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 for 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 when ingested in small quantities. 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 ssp., "Jack-o-lantern mushrooms," are another cause of sometimes significant toxicity. They are sometimes mistaken for chanterelles. Both are bright orange and fruit at the same time of year, although Omphalotus grows on wood and has true gills rather than the veins of a Cantharellus. They contain 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 "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 also 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.

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 and the deaths cannot be definitively attributed to mushroom consumption.

However, mushroom poisoning is not always due to mistaken identity. For example, the highly toxic ergot (Claviceps purpurea), which grows on rye, is sometimes ground up with rye, unnoticed, and later consumed. This can cause devastating, even fatal effects, which is called Ergotism.

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.