Hallucinogenic Mushroom Toxicity

Updated: Jan 23, 2021
  • Author: Louis Rolston-Cregler, MD; Chief Editor: Sage W Wiener, MD  more...
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Practice Essentials

For the most part, mushrooms with significant psychoactive effects fall into the following 2 groups [1] :

  • Mushrooms containing ibotenic acid and muscimol (isoxazoles) – Amanita gemmata, Amanita muscaria (also called fly agaric or soma), and Amanita pantherina (also called panther or panther amanita); these are not to be confused with the deadly Amanita phalloides, Amanita verna, and Amanita virosa.

  • Mushrooms containing psilocybin – Psilocybe caerulipes, Psilocybe cubensis, Gymnopilus spectabilis, Panaeolus species (eg, Panaeolus foenisecii), and Psathyrella foenisecii

The timing of symptom onset is important for distinguishing life-threatening or severe mushroom poisonings from less serious poisonings (eg, those involving hallucinogenic mushrooms), which typically have an onset of symptoms well within 5 hours of ingestion. If symptoms such as vomiting, diarrhea, and abdominal pain begin 5 hours or more after ingestion, mushrooms that can cause potentially life-threatening or severe toxicity (eg, A phalloides or Cortinarius spp) should be considered (see Presentation).

No particular diagnostic procedures are available or needed for most patients. Laboratory studies can be helpful in identifying complications of hallucinogenic mushroom abuse. Identification of the mushroom by a mycologist is desirable (see Workup).

Care is primarily supportive. Symptoms usually subside in 6-8 hours, though some may take as long as several days to resolve fully. Benzodiazepines may be used for sedation and treatment of panic attacks, hallucinations, and seizures. Psychiatric consultation and evaluation may be needed in some cases (see Treatment).

For patient education resources, see the Poisoning and Activated Charcoal.




Hallucinogenic mushroom toxicity is not a new phenomenon: Hallucinogenic fungi have been used in divinatory or religious contexts for at least 3000 years. However, it was not until the 1950s that the involved species of fungi were identified and the chemical nature of the active substances was determined. [2]

Consumption of hallucinogenic mushrooms continues to be popular today in some settings. Motives for their use include simple experimentation; a desire to enhance routine experiences, emotions, or social interactions; to disconnect from reality; to induce visions; as a psychotherapeutic tool; or for mystical or spiritual reasons. [3]

For centuries, Amanita muscaria has been consumed in central Asia as a hallucinogen. Some Siberian tribes report that 3 fresh A muscaria mushrooms can be lethal, whereas others claim that eating as many as 21 of these mushrooms is safe. Various hallucinogenic mushrooms containing ibotenic acid and muscimol or psilocybin are found in the New World. Reports of toxicity associated with this group of mushrooms have increased as a consequence of their growing popularity as hallucinogens. [4]



A muscaria, A pantherina, and A gemmata contain ibotenic acid, muscimol, and muscazone. These isoxazole derivatives are present in various concentrations, depending on environmental conditions, the maturity of the fungus, and the season of the year. Ibotenic acid and muscimol are relatively stable: Toxic activity has been maintained in dried plants for as long as 7 years.

Other toxins are probably present in these mushrooms; pure extracts of ibotenic acid or muscimol do not reproduce all of the symptoms observed after their ingestion. Although muscarinic acid originally was isolated from A muscaria, as the name suggests, muscarine does not appear to be of particular clinical significance in A muscaria poisoning; in fact, anticholinergic findings may be observed in this setting. A muscaria also lacks the amatoxins seen in other Amanita species.

Ibotenic acid resembles glutamic acid and is an agonist at central glutamic acid receptors; its decarboxylated derivative, muscimol, is an agonist at gamma-aminobutyric acid (GABA) receptors. The central effects of these hallucinogenic mushrooms are thought to be attributable to these actions. [2] Both ibotenic acid and muscimol can cross the blood-brain barrier. [5]

Many of the central nervous system (CNS) effects of muscimol (eg, sedation) are ascribed to its ability to act as a GABA agonist. By comparison, ibotenic acid is more of a CNS stimulant, by virtue of its action on glutamic acid receptors. In humans, most of the ibotenic acid ingested is excreted unchanged in the urine, with only some of it being metabolized to muscimol. About one third of the muscimol ingested is excreted unchanged, another third is conjugated, and the remaining third is oxidized. [5]

The Psilocybe, Gymnopilus, Panaeolus, and Psathyrella species previously mentioned (see Background) contain the indoles psilocybin and psilocin. Psilocin and its phosphate ester, psilocybin, are similar in structure to lysergic acid diethylamide (LSD). They are structural analogues of serotonin (5-hydroxytryptamine [5-HT]); thus, hallucinogenic effects probably are mediated through effects on serotonergic receptors. [2]



Hallucinogenic mushroom toxicity is caused by ingestion of fungi containing ibotenic acid, muscimol, psilocybin, or psilocin. Circumstances that could lead to such ingestion include the following:

  • Adults and adolescents seeking to achieve a state of intoxication – This is the most common reason for ingesting these mushrooms [1]

  • Incorrect mushroom identification by a naive forager (eg, a novice mushroom harvester or an immigrant who mistakes a local poisonous variety for an edible variety native to his or her homeland)

  • Intentional ingestion by a suicidal person

  • Unintentional ingestion by a child who found mushrooms growing in yards or outdoor play areas

  • Foul play, in which an individual is poisoned by someone else

  • Inadvertent poisoning from dried mushrooms purchased on the Internet or from other sources where the composition of the mushroom is unreliable or where the mushroom might be contaminated with unknown toxic compounds



Determination of the frequency of hallucinogenic mushroom toxicity is limited by the lack of a national reporting system or registry for mushroom poisoning and by the likelihood that many affected individuals may never seek medical attention. However, estimates based on small studies or surveillance systems using self-reporting are available.

In a study of 174 adolescents with a history of substance abuse, 45 (26%) reported having used hallucinogenic mushrooms at some point in their life, often in combination with alcohol or marijuana. [6]

On the basis of data collected from September 2008 to December 2009, the Youth Risk Behavior Surveillance System reported that 8% of students had used a hallucinogenic drug (eg, LSD, phencyclidine [PCP; angel dust], mescaline, or mushrooms) at least once in their life. [7] Hallucinogen use was more common among males and whites than among females and African Americans and Hispanics.

In 2019, 5415 mushroom ingestions were reported to the National Poison Data System of the American Association of Poison Control Centers (AAPCC). Mushrooms of unknown type were involved in 79% of reported ingestions. Mushrooms containing psilocybin and psilocin accounted for 590 cases, with 387 involving single-substance exposures but no deaths were reported; 27 exposures (7%) involved children younger than 6 years. About 86% of all cases of psilocybin and psilocin mushroom poisoning resulted from intentional ingestion, and 80% were treated at a healthcare facility. [8]

Of the 30 cases of single-substance exposure to ibotenic acid−containing mushrooms reported by US poison control centers through the AAPCC in 2019, 43% were intentional ingestions.  The majority (57%) of exposures were adults ages 19 years and older. [8]

The overall prevalence levels of hallucinogenic mushroom use in Europe have been generally low and stable for a number of years. Among adolescents and young adults (ages 15–34), in 2018 prevalence estimates of less than 1% were reported with the exception of the Netherlands (1.9 %), Finland (1.9 %) and the Czech Republic (3.1 %). [9]

Few data exist on the age distribution of hallucinogenic mushroom users; however, some general observations may be made.

Adults are frequently involved as foragers for edible mushrooms; because of errors in identification, they may ingest toxin-containing lookalike mushrooms. Adults and adolescents may also be poisoned when they intentionally consume mushrooms, picked from the ground or purchased dried, to achieve intoxication. In particular, college students are known to abuse psilocybin mushrooms. [10, 11, 12]

Young children may experience mushroom poisoning when they eat mushrooms found outside, typically in yards or outdoor play areas. Reports of seizurelike activity have been reported for children but are not typical in adults. [13, 14]  



Use of hallucinogenic mushrooms rarely results in life-threatening symptoms. [15] The prognosis is generally excellent. Many patients who ingest these mushrooms exhibit only minor symptoms or no symptoms at all. Symptoms typically are mild to moderate in severity and self-limited, though some effects of ibotenic acid poisoning, particularly headache, may take 2 days or more to resolve. [13, 14] Patients commonly recover without drug therapy. Fatalities from hallucinogenic mushroom poisoning are rare.

One case series of 14 accidental ingestions by young children (mean age of 3 years) found that the typically small amounts of Panaeolus foenisecii ingested (1-5 mushrooms) did not lead to clinically significant symptoms. [16]

From 1999 to 2009, 35 deaths due to mushrooms were reported to US poison control centers through the AAPCC, and 1 death was attributed to mushrooms containing ibotenic acid. [17] The patient who died was a 44-year-old man who ate 6-10 freeze-dried mushrooms, purported to be A muscaria, which he obtained from the Internet. Paramedics found him in cardiac arrest, and he eventually died 10 days later with anoxic brain injury. The report did not mention whether and how the mushroom was confirmed to be A muscaria.

In 2019, no deaths were reported by the AAPCC from ingestion of mushrooms containing psilocybin and psilocin; major effects were seen in 1% of cases. Moderate effects were reported in 41% of the 387 single-substance exposures and 29% reported no or mild effects. The outcome was unknown in 29% of reports. Of the 30 cases of single-substance exposure to ibotenic acid−containing mushrooms reported by US poison control centers through the AAPCC in 2019, 40% had no or minor effects, 20% had moderate effects, 7% had major effects, and 33% had unknown outcomes. [8]

In Slovenia, a 48-year-old man consumed several A muscaria mushrooms and began to experience vomiting and lethargy within 30 minutes. [18] He was found comatose, having a seizurelike episode; he then awoke and was oriented 10 hours after ingestion. By 18 hours after ingestion, the patient’s condition had deteriorated, and he became confused and uncooperative. Paranoid psychosis with visual and auditory hallucinations appeared, persisted for 5 days, and resolved with short-term drug therapy, without any subsequent recurrence.

In Poland, 5 young adults aged 18-21 years consumed dried A muscaria and a can of beer, and 4 of the 5 experienced heightened visual and auditory perceptions beginning about 20 minutes after ingestion. [19] Of these 4, 1 experienced severe hallucinations and lost consciousness, according to the others, who induced vomiting and gave her liquids. The next day, this person came to a hospital complaining of tiredness and gastric pain. She was evaluated, observed for several days, and sent home. No confirmation of the mushrooms was performed.

Also in Poland, 2 women ate 5 fried caps of A pantherina (later confirmed) and developed nausea, stomachache, diarrhea, and vomiting within 2 hours. [20] They subsequently developed ataxia, waxing and waning obtundation, altered perceptions, hyperkinetic movements, and altered speech. One patient’s symptoms lingered for several days, whereas the other had no symptoms at 6 hours after ingestion; the latter received activated charcoal and intravenous (IV) fluids.

In a series of 9 children aged 1-6 years who ingested A muscaria or A pantherina and were treated at a hospital in Seattle, Washington, symptoms developed within 30-180 minutes (median, 45 minutes) after ingestion and lasted for 4-14 hours (median, 9 hours). [13] Symptoms included lethargy (4 children), unresponsiveness (1), comalike sleep (1), ataxia (2), abnormal movements (3), tonic-clonic seizures (3), and agitation, babbling, or hysteria (5). All 9 children recovered uneventfully within 12 hours after admission.

In addition to CNS sequelae, hallucinogenic mushrooms may affect other organ systems. In one case of psilocybin intoxication, an 18-year-old man developed a cardiac dysrhythmia and myocardial infarction. [21]   Another case report described a 25-year-old man who developed rhabdomyolysis and acute renal failure followed by posterior encephalopathy and cortical blindness after ingesting hallucinogenic mushrooms. [22]