Mushroom poisoning from amatoxins (death cap): symptoms, danger and emergency care

Mushrooms and toadstools are the fruiting bodies of fungi. Patient.info’s reference article notes there is no real difference between the two words; toadstool has gradually become applied to toxic types. Most mushrooms found in gardens or on lawns are highly unlikely to be seriously toxic, although they may cause stomach upset or hallucinations.

The most dangerous toxins are the amatoxins. The article says they are produced by Amanita phalloides, the death cap, and cause necrosis (cell death) of the liver and, to a lesser degree, the kidney. The equally toxic Amanita virosa occurs in the birch woods of the north. The death cap is found in all areas of the UK with the possible exception of Sutherland and Western Ross.

Identifying mushrooms is difficult. Patient.info describes it as an exact and time-consuming science and notes that even experienced mycologists may not be able to separate edible from poisonous species without microscopic examination.

The key feature is delay. Patient.info says that mushrooms which cause symptoms within six hours of eating are unlikely to be seriously toxic, whereas a long latency of more than six hours signals a serious ingestion that should be considered potentially life-threatening. In amatoxin poisoning symptoms typically begin 6 to 24 hours after the meal.

The first phase is gastrointestinal: violent vomiting, diarrhoea and abdominal pain. People may then seem to recover. A few days later, hepatic failure and acute kidney injury can develop. In severe cases there may be jaundice, bleeding and confusion. Dehydration and low blood sugar are common complications.

• Severe vomiting, watery diarrhoea and abdominal cramps starting many hours after a mushroom meal.

• Apparent improvement after a day or so, which should not be taken as the all-clear.

• Later yellowing of the skin or eyes, bleeding or bruising, confusion or drowsiness.

• Reduced urine output or other signs of kidney trouble.

The NHS says to get medical advice immediately if you think you or someone else has been poisoned, and that symptoms may take a few hours or days to start. It says to call 999 or go to A&E if you think someone may have swallowed, touched or breathed in something harmful, and to call NHS 111 if you are not sure whether something is harmful.

While waiting, the NHS advises finding what caused the poisoning and taking some of it, or its packaging, to show the doctors at the hospital. For a wild mushroom this means keeping any remaining mushroom, or a photograph, for identification, and if the person is sick, collecting a sample of the vomit in a container. Do not try to make someone sick and do not give them anything to eat or drink.

Do not wait for symptoms. The NHS notes that if there are no symptoms treatment may not be needed, but the person may still need to be monitored for several hours in case they become unwell, and with slow-acting mushrooms that monitoring matters even if they feel well.

The history is crucial: what was eaten, how much, when, and whether others shared the meal. Patient.info says that every effort should be made to identify the mushroom, that the clinical toxicology database TOXBASE has descriptions and photographs to help, and that in the UK the National Poisons Information Service can be contacted for advice.

Blood tests assess liver and kidney function and clotting. The article notes that urinary amanitin analysis is a valuable diagnostic tool. Doctors will observe people for at least six hours to exclude other toxicity.

There is no single reliable antidote, and care is supportive. Patient.info lists correction of low blood sugar and electrolyte disturbance, gastric lavage and activated charcoal (with some evidence that multiple doses may help in amanita poisoning because the toxins undergo enterohepatic circulation), and fluids. It says N-acetylcysteine is sometimes used for liver injury but that evidence is limited, and that animal and anecdotal evidence suggests possible benefit from penicillin, silibinin and other agents.

Fulminant liver failure may require a liver transplant. The article says factors linked to a poor outlook include low blood pressure, encephalopathy, bleeding, low urine output, low blood sugar and very abnormal clotting tests.

Patient.info says that the prognosis in the great majority of cases of mushroom poisoning is excellent, but amatoxin poisoning is different. With good supportive care, mortality may be reduced from 60 per cent but, because of progressive liver failure, is still high at 5 to 20 per cent.

The article also notes that poisoning with other toxins, such as the orellanine in some Cortinarius species, can cause kidney failure that appears from 36 hours to 2 weeks after eating, and that most people recover from gyromitrin poisoning, so the type of mushroom matters to the outlook.

The advice from the professional reference is blunt: do not take risks with wild mushrooms and keep children well away from them. Identification is an exact and time-consuming science, and gourmet cooks who have harvested their own have been poisoned.

The safest course described in the article is to avoid wild mushrooms altogether, since identification errors can be fatal and symptoms are delayed.

Suspected poisoning is handled through emergency services and NHS emergency departments, which can seek advice from the National Poisons Information Service. The NHS says you will need to be treated in hospital for poisoning because it can make you seriously unwell and can be life threatening.

The first priority is emergency assessment, which is the same whichever service you reach first, and it is the hospital team that will decide whether specialist liver care is needed.