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Death Cap Mushroom Poisoning

Medically Reviewed by Mahammad Juber, MD on December 14, 2022

Sometimes it can be difficult to tell whether a plant is toxic or not based on its name alone. This isn’t the case with the death cap mushroom, which is as poisonous as it sounds. 

Although this mushroom is extremely dangerous, it can easily be confused with an edible mushroom, and symptoms of death cap poisoning can be mistaken for other conditions. When eating wild mushrooms, it's important to be absolutely sure what you’ve got before adding it to your meal.

What Is the Death Cap Mushroom?

The death cap mushroom, also known by its scientific name Amanita phalloides, is a type of fungus. Like other mushrooms, the death cap has a flat or slightly rounded cap that sits on top of a thick stalk.

Death caps can be seen throughout the world and are typically found in forests growing on or near trees.

Death caps are extremely poisonous — the toxins found in deathcaps and related mushrooms cause 90% of mushroom poisoning deaths worldwide.

How to Identify Death Cap Mushroom

Death cap mushroom identification can be tricky. Features of the death cap that distinguish it from related species may be overlooked by novice foragers.

Where is the death cap mushroom found? The death cap mushroom is native to Europe but is now distributed throughout the world. In the United States, death cap mushrooms are typically found on the East and West Coasts.

On the East Coast, death caps are found in small patches ranging from Maryland to coastal Maine. Death caps are more prevalent on the West Coast and can be found in large patches from Southern California to British Columbia in Canada.

When does it grow? Fungi like the death cap have large underground networks of fibers called mycelium that fruit, or produce mushrooms, at certain times of the year. Death cap mushrooms typically emerge in the spring, late summer, and fall.

Rainfall and temperature both have a big impact on mushroom growth. Periods of large rainfall and warm temperatures can cause larger blooms of these deadly mushrooms.

What does it look like? When mature, the death cap has a smooth top cap that may be white or yellow with a green hue. These mushrooms typically have a ring that surrounds the top of the stalk underneath the cap. 

Unlike similar mushrooms, the death cap has white gills under its cap that do not attach to its stalk. The death cap also has a large, bulbous cup at the base of its stem. This cup is typically underground and may be detached from the mushroom if it’s snapped off at the stalk.

Is the Death Cap Mushroom Poisonous?

The death cap mushroom is not toxic to touch but extremely poisonous when eaten. Death cap mushrooms have large concentrations of toxins that can be fatal even in small doses. 

What makes death caps poisonous? Death caps contain a high concentration of compounds called amatoxins. 

Amatoxins are a type of alkaloid, a naturally occurring chemical. Alkaloids are typically found in organic matter like plants and fungi. These chemicals are fairly common — morphine and nicotine are both types of alkaloids.

Unlike some alkaloids that are not harmful or are even beneficial to humans, amatoxins are extremely dangerous. These chemicals can stop protein synthesis in cells, causing the cells to die.

Are death caps only poisonous when eaten raw? Death cap mushrooms are poisonous regardless of how they’re prepared. The amatoxins in death caps are very stable and are not affected by heat or acids. Cooking, drying, or freezing these mushrooms has no effect on how poisonous they are.

Death Cap Mushroom Poisoning

Death cap mushroom poisoning is extremely serious and requires medical attention right away. Death cap mushroom symptoms typically progress through three stages.

Stage 1: Gastrointestinal Phase. The first stage of death cap mushroom poisoning usually happens between six and 24 hours after eating the mushroom. Typical symptoms of this first stage include:

  • Nausea and vomiting
  • Bloody diarrhea or urine
  • Abdominal pain
  • Fluid loss, dehydration, and electrolyte imbalance
  • Fever

Stage 2: Latent Phase. After 12 to 36 hours, the first wave of symptoms passes, and patients may begin to feel much better. However, during this stage, the toxins in the mushroom are still affecting the body and are beginning to damage the liver and kidneys.

Stage 3: Hepatorenal Phase. The final stage of death cap poisoning happens when the liver and kidneys are so damaged that they begin to shut down. This period is very dangerous and may require extreme medical intervention. 

Symptoms of the hepatorenal phase typically start three to six days after eating the mushroom and include:

  • Loss of liver and kidney function
  • Jaundice
  • Low blood sugar
  • Delirium and confusion

What to Do If You Have Death Cap Mushroom Poisoning

It can be difficult to diagnose death cap mushroom poisoning because its early symptoms may seem like another illness and the patient may seem to improve after early symptoms pass. 

If you have eaten wild mushrooms and begin to show any symptoms of poisoning, call your poison control center and seek medical attention right away. Alert medical professionals that you’ve eaten mushrooms recently and bring the mushroom with you if you can.

Treatment for death cap mushroom poisoning. Treatments for death cap poisoning vary depending on how long it's been since the mushroom was eaten. It is critical to receive treatment early to prevent liver and kidney damage.

Treatment in early stages of the poisoning focuses on stabilizing the patient and trying to counteract the effect of the toxin. These treatments may include: 

  • Pumping the stomach
  • Giving activated charcoal
  • Surgically removing parts of the mushroom
  • Administering fluids

If the patient is at an advanced stage of poisoning, extreme measures like a liver transplant may be necessary.

Safe Plants That Look Like Death Cap Mushrooms

Asian straw mushrooms and other edible species of Amanita look very similar to death cap mushrooms. Death cap mushrooms can be distinguished from similar species by the large, bulbous cup at the base of the stalk. 

When picking mushrooms, it may be tempting to snap the mushroom off at the stalk instead of digging the full mushroom out from the ground. Since the death cap is most easily distinguished by the bottom of its stalk, it’s important to pull the full mushroom out of the ground to confirm that you’ve picked an edible relative and not the poisonous death cap. 

Don’t eat any mushrooms that you’re not sure about. It’s better to be safe than sorry. If you have a mushroom that looks like a death cap but can’t confirm what kind of mushroom it is, have it identified by a mycologist before eating, or opt for a different mushroom. 

Death caps are commonly found in forests but have shown up in urban and suburban areas. If you find mushrooms in your backyard, be sure to confirm what kind of mushroom they are before eating them.

Show Sources

SOURCES: 
Brandeis University: “Mushroom Tutorial.”
British Columbia Centre for Disease Control: “Death Cap Mushrooms.”
Centers for Disease Control and Prevention: “Amanita phalloides Mushroom Poisonings — Northern California, December 2016.”
Encyclopedia Britannica: “Alkaloid.”
Food and Chemical Toxicology: “Amanita phalloides poisoning: Mechanisms of toxicity and treatment."
New Phytologist: "Distribution and abundance of the introduced ectomycorrhizal fungus Amanita phalloides in North America.”
Vancouver Mycological Society: “Amanita phalloides.”

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