Amanita smithiana

Safety first. Amanita smithiana and Amanita proxima are poisonous wild mushrooms. They cause stomach illness (nausea and vomiting), usually within hours, and then acute kidney failure that appears one to several days after the meal. [3][4][6][7] Some people feel better in between, so feeling well after the first illness is not a sign of safety. If anyone may have eaten a wild or unknown mushroom, call Poison Help now at 1-800-222-1222 (US), even if there are no symptoms. A poison control centre says not to wait for symptoms, because serious damage may already be done when they appear. [1] Call 911 if the person collapses, has a seizure, has trouble breathing or cannot be woken. [2] Outside the US, call your local poison centre or emergency number; see poison help by country. This page gives no identification help and no way to tell safe from unsafe mushrooms. See mushroom poisoning: warning signs and urgent help.

The short version. These are not food, not a medicine and not a supplement. Reports from the Pacific Northwest describe people who thought they were eating the prized pine mushroom (American matsutake) and ended up on dialysis. [4][5] In the published cases we read, kidney function came back with supportive care, including temporary dialysis. [3][4][5][6][7] That is much better than the outcome after the deadly webcap, but dialysis is still a major, frightening illness, and the reports are case reports, so they cannot tell us how often the poisoning goes badly. There is no antidote. [8][9] No safe amount of either mushroom is known.

What they are

• Amanita smithiana is reported mainly from western North America (the Pacific Northwest, the United States and Canada). [3][9] Reports describe it as the cause of a "new pattern" of mushroom poisoning in which kidney failure is the main problem, not liver failure. [3]
• Amanita proxima is reported from the Mediterranean area, with poisonings described in southern France and Israel. [6][11][12][13]
• A 2026 paper attributes most kidney injury from mushrooms of the genus Amanita to species in section Roanokenses, and lists both of these among the nephrotoxic species of Europe and North America, together with A. punctata, A. boudieri, A. gracilior and A. echinocephala. [10] The same paper describes these amanitas as very similar to one another and hard for non-specialists to tell apart. [10]
• Wikidata lists the two species as Q1947219 and Q3613611. [14] Their poison is not the amatoxin of the death cap and destroying angel, and not the orellanine of the deadly webcap; see death cap, destroying angel and deadly webcap.

Do not identify wild mushrooms from text, photos or apps

Even very experienced gatherers can find it hard to tell safe wild mushrooms from poisonous ones, and amanitas can look very like edible kinds, according to a poison control centre. [1] The same centre says an animal eating a mushroom is not proof it is safe for people, and advises eating only mushrooms bought from a shop. [1] See also cooking edible mushrooms safely. We give no description of these mushrooms on purpose.

The toxin and how it acts

• A. smithiana toxin. A 2025 review names the toxin as an "allenic norleucine" and says it causes stomach illness and delayed kidney failure. [8] An amino-acid-type compound is what that name suggests, but we did not open the original chemistry papers, so we give no structure. A 2013 case report says the chemical structure of the toxin was unknown to its authors and that laboratories can spot it as a characteristic spot on thin-layer chromatography, a simple separation test. [5] A 2015 case report adds that this test is not entirely specific. [7]
• What it does to the kidney. Kidney biopsies in patients poisoned by related white amanitas showed acute interstitial nephritis (inflammation of the tissue between the kidney tubes) and tubular necrosis (death of tubule cells). [6] The poisoning is called "Amanita nephrotoxic syndrome" when it comes with early stomach symptoms, mild hepatitis and severe but reversible kidney injury. [7]
• Other species carry it. In herbarium tests, the smithiana toxin was found in A. boudieri, A. gracilior and A. echinocephala, so poisonings by other white amanitas can look just like it. [6]
• ***A. proxima* may be different.** The same tests could not detect the smithiana toxin in A. proxima, even though its poisoning looks similar. [6] Its toxin has not been identified in the sources we read.
• Cooking. In one case report, the toxin was still detected in leftover cooked soup made with the mushrooms. [5] We found no source testing cooking, freezing or drying systematically, so assume none of them makes a poisonous mushroom safe. [1]
• It is not amatoxin. The causal toxin differs from amatoxin, the death-cap poison. [7] That matters in the emergency room: one patient was first treated as though he had amatoxin poisoning, and his kidney failure did not respond. [3]

Symptom timeline

Reports differ in the exact hours, so treat these as ranges, not a guide to when it is "safe".

1. Stomach phase: nausea, vomiting and sometimes diarrhoea. Reports give onset from 20 minutes to 12 hours (four US patients) [4], 2 to 12 hours with a median of 6 (as summarised in a 2015 case report) [7], within 6 hours (a US case) [3], and 10 to 12 hours (three European patients with related white amanitas) [6]. A 2025 review gives 30 minutes to 3 hours. [8]
2. Mild liver signs: liver blood tests rose slightly and peaked about a day after the meal in one case. [3] Reports of the related syndrome call the hepatitis mild. [6][7]
3. Kidney phase: kidney injury was seen about one day after the first illness in a US case [3] and 2 to 6 days after eating in a summary of earlier cases [7]. Four US patients arrived in kidney failure 4 to 6 days after eating. [4] A 63-year-old man arrived with no urine output two days after a wild-mushroom soup. [5] A 2025 review says kidney failure comes 12 to 24 hours after the stomach phase. [8]
4. Why it matters: kidney failure can show only days after the stomach illness [3][4], so tell clinicians about any wild-mushroom meal even if it was days ago.

Treatment as described by medical sources

• There is no antidote. Treatment is supportive: monitoring, fluids and kidney replacement (dialysis) while the kidneys recover. [8][9]
• Dialysis. In the case reports, patients had temporary haemodialysis for days to weeks. One patient was on dialysis from day 4 and had the catheter removed 39 days after the meal [3]; four US patients needed it for at least several weeks [4]; a 63-year-old man recovered kidney function after nine days of supportive care and went home 15 days after eating. [5]
• Recovery. In the reports we read, kidney function returned to normal or baseline. [3][4][5][6] A 2015 report says kidney recovery was complete in all earlier cases it cited. [7] This is from case reports, which favour the cases that were written up.
• Treatments for other poisons did not help. In one case, N-acetylcysteine, penicillin and milk thistle extract were started because amatoxin poisoning was suspected, and the kidney failure did not respond. [3] Do not try these yourself.
• Organ transplant is described by a 2021 review as reserved for cases where dialysis fails, in nephrotoxic mushroom poisoning generally. [9]
• No home remedies. Follow whatever the poison centre or a clinician tells you. See what to do first for any poisoning and what to tell Poison Help when you call.
• Tell the doctors what was eaten, when, and how many people shared it. A poison centre advises keeping a piece of the mushroom to show responders. [1]

Amanita proxima: extra reports

• A French report calls the southern-France picture "proximien syndrome": early stomach trouble, mild liver enzyme rise and late kidney impairment. [12] The first child case (an 11-year-old boy) needed dialysis and recovered fully; his mother, who ate less, had only blood-test changes in the kidneys and liver. [11]
• Two French observations described severe heart problems after A. proxima, treated with symptomatic care with good outcomes. [12] The authors suggest checking the heart early in such poisonings.
• A 2026 review of poison-centre data from Israel lists A. proxima among the species behind moderate-to-severe cases. [13]
• Because A. proxima has no confirmed smithiana toxin [6], statements about one species should not be assumed to hold for the other.

Which edible mushrooms are named in poisoning reports

This is the history of mistakes, not a way to avoid them. In US reports, people believed they were eating the American matsutake or pine mushroom (Tricholoma magnivelare), a prized wild food. All four patients in a 1998 series thought so [4], and a 2013 case report describes the same kind of mix-up. [5] Our matsutake page covers that mushroom and the safety of wild harvest. We found no reported edible mix-up for A. proxima in the sources we opened. Never rely on a photo, description or app. [1]

Epidemiology

• A 2009 report describes a "new pattern" of mushroom poisoning in the Pacific Northwest led by kidney failure. [3] A 2021 review counts A. smithiana among newly recognised nephrotoxic species in the United States and Canada, and A. proxima in Europe. [9]
• Mortality is described as rare in a 2025 review. [8] We found no recent national count of cases that we could open. Treat all figures as partial.
• The 2012 European report says the poisoning is clinically distinct from the delayed, often irreversible webcap kidney failure. [6]

Lab data and chemistry

Wikidata (the open knowledge base behind the LOTUS natural-products project) lists no compounds for Amanita smithiana and none for A. proxima in the file we received. [14] A listing would mean "reported in at least one study of this species". This section describes a poison, not a health benefit.

A. What the laboratory literature reports in these mushrooms

B. Measured values

The patient tests are clinical blood tests, not measurements of the mushroom.

C. What the numbers do and do not mean

• We found no open measurement of the toxin in the mushrooms, so no one can say how much is in a mushroom, how much is harmful, or how much varies between mushrooms or places.


• The tests that detect the toxin in hospitals and herbarium collections (thin-layer chromatography) are about confirming the cause afterwards and are not a way to check a mushroom before eating. [5][6][7]


• Blood creatinine and urea show how badly the kidneys are working. A high value is a sign of kidney injury and not a measure of how much was eaten.


• Nothing here suggests health benefits. Different countries' reports use different species names, and A. proxima's toxin is not known. [6]

Related pages

• Mushroom poisoning: warning signs and urgent help
• Mushroom safety quick reference: emergency and who to call
• Cooking edible mushrooms safely
• Matsutake, the prized food mushroom named in US mix-up reports
• Deadly webcap, another kidney poison with a different timeline
• Mushrooms and the kidneys, oxalates and the liver
• Plant and mushroom poisoning