Deadly Webcap

Safety first. The deadly webcap and the fool's webcap are poisonous wild mushrooms. They contain orellanine, a toxin that damages the kidneys. Stomach symptoms usually start only a few days after eating, and kidney failure can follow up to about two weeks after the meal, so a person can feel well for days after a dangerous meal. [3][6] 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. Poison centers say not to wait for symptoms, because they may not appear for several days. [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 and the mushroom safety quick reference.

The short version. These are not food, not a medicine and not a supplement. Orellanine is not destroyed by cooking, freezing or drying. [4][5] There is no antidote; care is supportive and, when the kidneys fail, centres on dialysis. [3][5][6] A published review puts deaths at about 5.5% of well-documented cases, and many survivors are left with long-term kidney damage. [3][6] Most poisonings happen when a foraged basket is mistaken for an edible mushroom. [3][9]

What they are

Cortinarius rubellus is called the deadly webcap, and C. orellanus the fool's webcap. [3] Wikidata lists Cortinarius speciosissimus, a name that appears in many older medical reports, as a synonym of C. rubellus. [14] They belong to the large webcap genus Cortinarius; they are woodland mushrooms of Europe and North America. [3][5] Not every webcap is poisonous, and we give no way to tell them apart. Orellanine has not been found outside this genus, and only in some of its members. [3]

Do not identify wild mushrooms from text, photos or apps

Even very experienced gatherers can find it hard to know whether a mushroom is safe, according to a poison control centre. [1] In a 2026 study that tested 12 phone applications on mushroom photos, several species were misidentified or missed, especially when the mushroom was partly hidden or immature. [12] The mushroom safety quick reference says the same. Only buy mushrooms from a shop, or have a trained local expert check every mushroom, one by one, before eating. A mushroom that animals have eaten is not proof it is safe for people. [1]

The toxin and how it acts

• Orellanine. The toxin is called orellanine. It was first linked to poisoning after a mass poisoning in Poland in the 1950s, and isolated in 1962. [3] Sources give different counts for that event (135 people in one review; 144 patients and 25 deaths in another), so we give no single figure. [3][5]
• Where it acts. In animals and in kidney samples from poisoned people, it harms the cells of the proximal tubule, the part of the kidney that reclaims useful substances from filtered blood. [3] The exact way it does this is still debated; oxidative damage is the main idea. [3][4]
• Its breakdown products. Light turns orellanine into orellinine, which is also toxic, and then into orelline, which is not. [3][5]
• Cooking. Orellanine does not break down below about 150 degrees C. Cooking, freezing and drying do not remove the toxicity. [3][4][5]
• In a meal. In a chemistry test, a mushroom stew made from edible mushrooms with a single webcap added still contained measurable orellanine. [8] One wrong mushroom can spoil the whole dish.

Symptom timeline

Timing varies a great deal from person to person. [3]

1. First hours to day 3: often nothing noticeable. Stomach symptoms (nausea, vomiting, diarrhoea, stomach pain) usually begin around day 3 (median 3 days in a review of 90 detailed cases). [3][6] Thirst, headache, chills, tiredness and muscle aches can come with them. [4] Reviews give a quiet period of about 2 to 6 days before the illness, and one case report gives kidney failure 2 to 20 days afterwards. [4][10]
2. Kidney phase: back or flank pain, intense thirst, passing very little urine (or sometimes too much), then kidney failure; reviews give a median of about 8 to 8.5 days and a range up to about 2 weeks or more. [3][4][6] Some patients have mild symptoms that fade, which can leave the poisoning unnoticed. [4]
3. Why it is missed: people often arrive only when the kidneys have failed, when mushrooms are no longer an obvious cause. By then the toxin can no longer be found in blood or urine, and a kidney biopsy is often the only way to confirm. [3] People sometimes eat the same mushrooms again in the days before symptoms appear. [5]

Because "feeling fine" does not mean safe, call the poison centre as soon as a wild mushroom may have been eaten. [1]

Treatment as described by medical sources

• There is no antidote. Treatment is supportive. [3][5][6]
• Dialysis. Standard care is dialysis to relieve the kidneys while they try to recover. [3] Some people need a kidney transplant. [5][6][7]
• Other ideas. Antioxidants, steroids or N-acetylcysteine have been tried, but results have not been consistent enough to call them standard. [3][5] Do not try them yourself.
• No home remedies. Do not try home treatments. 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. Say what was eaten, when, and how many people shared the meal. Keep the leftovers or a sample only if the poison centre asks you to.

How serious is it? What studies report

These figures come from different case collections and are not directly comparable. Reports tend to include the severe cases, so the real range of outcomes is not known. Reviews also describe individual differences, including age, pre-existing kidney disease and the amount eaten. [4]

Which edible mushrooms are named in poisoning reports

This is the history of mistakes, not a way to avoid them. A review says people most often eat these mushrooms believing them to be an edible kind, and names two: the yellow foot (Craterellus tubaeformis) and the golden chanterelle (Cantharellus cibarius). [3] A 2025 paper says foragers have confused the yellow foot with the deadly webcap and that people are treated in Sweden every year for this mistake; the webcap can grow in the same places, sometimes among yellow foot. [9] A 2012 chemistry study used yellow foot for the same reason. [8] In Norway, mushroom checkers have discarded whole baskets of yellow foot because a webcap was found among them. [9] This site's yellow foot, chanterelle and blewit pages cover the safety of those edible mushrooms; the blewit page names webcaps among possible mix-ups. These pages do not teach identification either.

Reports also describe people eating the mushroom for the second time before the first symptoms arrive. [5]

Epidemiology

• Cases are reported mainly in Europe and North America, with some in Australia. [5]
• The first Scottish cases were reported in 1979; the authors called for warnings about the genus in books on wild foods. [15]
• Most poisonings are unintentional. [5]
• We found no recent count of cases for any single country that we could open. Treat all counts as partial.

Lab data and chemistry

Wikidata (the open knowledge base behind the LOTUS natural-products project) lists 6 compounds for Cortinarius rubellus and 2 for C. orellanus; none of the statements has a paper attached in the file we received. [13] A listing means "reported in at least one study of this species". This section describes a poison. It shows nothing about health benefits.

A. What the laboratory literature reports in these mushrooms

The toxin sits in the mushroom mainly as its sugar-bound forms, and these turn back into orellanine in acid or in water extracts, which makes measuring hard. [3][8]

B. Measured values

The two content values are quoted by a 2024 review from an earlier paper (Karlson-Stiber and Persson, 2003); we did not open the original. No USDA entry exists, as this is not a food. We found no open measured value for heavy metals, triterpenes or beta-glucan, and we did not look for any, as they are not relevant here.

C. What the numbers do and do not mean

• A content figure is an average from one set of dried samples. Toxin levels differ between samples, places and years, so no size or amount of a poisonous mushroom can be called safe. [4]


• Heating does not destroy orellanine, so a "cooked" mushroom is not safer. [3][4][5]


• The tests used in clinics have trouble finding orellanine once symptoms start, because the toxin leaves the blood while the kidneys hold it. [3][5]


• Orellanine has been studied in the laboratory as a possible cancer treatment, because it acts on kidney cells; a review says early human trials were announced for 2022. This is research on a purified molecule, not on the mushroom, and it gives no reason to eat the mushroom. [3]

Related pages

• Mushroom poisoning: warning signs and urgent help
• Mushroom safety quick reference: emergency and who to call
• Cooking edible mushrooms safely
• Yellow foot, chanterelle and blewit
• Mushrooms and the kidneys, oxalates and the liver
• Plant and mushroom poisoning