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Chemical Food Poisoning

By Gerald F. O’Malley, DO, Thomas Jefferson University and Hospital ; Rika O’Malley, MD

Chemical food poisoning results from eating a plant or animal that contains a toxin.

  • The poisoning occurs after ingesting poisonous species of mushrooms or plants or contaminated fish or shellfish.

  • The most common symptoms are diarrhea, nausea, and vomiting and sometimes seizures and paralysis.

  • The diagnosis is based on symptoms and examination of the ingested substance.

  • Avoiding wild or unfamiliar mushrooms and plants and contaminated fish reduces the risk of poisoning.

  • Replacing fluids and ridding the stomach of the toxic substance are the best forms of treatment, but some substances are deadly.

Many disorders cause sudden vomiting and diarrhea due to inflammation of the digestive tract (gastroenteritis—see Gastroenteritis). Sometimes people loosely refer to all of these disorders as "food poisoning." However, most vomiting and diarrhea is caused by a digestive tract infection from a virus or bacteria. Only gastroenteritis caused by a toxin that was eaten is true food poisoning. For example, bacteria in contaminated food can produce such toxins (see Staphylococcal Food Poisoning). Also, although many poisonous plants, mushrooms, and seafood cause digestive tract symptoms, some affect other organs.

Mushroom (Toadstool) Poisoning

Many species of mushroom are poisonous. The potential for poisoning may vary within the same species, at different times of the growing season, and with cooking. It is difficult to differentiate poisonous from nonpoisonous mushrooms in the wild, even for highly knowledgeable people. Folklore rules are unreliable.

All poisonous mushrooms cause vomiting and abdominal pain. Other symptoms vary greatly depending on mushroom type. Generally, mushrooms that cause symptoms early (within 2 hours) of ingestion are less dangerous than those that cause symptoms later (usually after 6 hours).

Mushrooms that cause early gastrointestinal symptoms (such as Chlorophyllum molybdates and the little brown mushrooms that often grow on lawns) cause vomiting and diarrhea. The diarrhea is occasionally bloody. Some people have headaches or body aches. Symptoms usually go away within 24 hours.

Mushrooms that cause early symptoms that affect the brain and spine include hallucinogenic mushrooms, which contain the hallucinogen psilocybin. The most common are members of the Psilocybe genus, but some other mushrooms also contain psilocybin. Symptoms begin within 15 to 30 minutes of ingestion and include euphoria, enhanced imagination, and hallucinations. A rapid heart beat and high blood pressure often develop, and some children develop a fever. However, these symptoms go away without treatment, and serious consequences are rare, so specific treatment is usually not needed. However, if the person is very agitated, the doctor may give a sedative (such as lorazepam).

In poisoning caused by many species of Inocybe and some species of Clitocybe, the toxic substance is muscarine. Symptoms, which begin within 30 minutes after eating, may include increased tearing and salivation, narrowing (constriction) of the pupils, sweating, vomiting, stomach cramps, diarrhea, dizziness, muscle twitching (fasciculations), confusion, coma, and, occasionally, seizures. Symptoms are usually mild and usually go away within 12 hours. Doctors give atropine by vein (intravenously) to people who have severe symptoms, and nearly all people recover in 24 hours. Without treatment, death can occur in a few hours with severe poisoning.

Mushrooms that cause delayed gastrointestinal symptoms include Amanita phalloides and related types of mushroom (members of the Amanita,Gyromitra, and Cortinarius genera). Amanita phalloides causes 95% of mushroom poisoning deaths. Vomiting and diarrhea start in 6 to 12 hours. Sometimes the blood sugar level drops dangerously low. Symptoms subside for a few days, but then people develop liver failure and sometimes kidney failure. Liver failure causes the skin to turn yellow (jaundice). People with kidney failure may have reduced urination or may have stopped urinating. Sometimes the symptoms disappear on their own, but about half of the people who have this type of poisoning die in 5 to 8 days. People with liver failure may survive if given a liver transplant.

Amanita smithiana mushrooms tend to cause delayed vomiting and diarrhea (about 6 to 12 hours after they are eaten). Kidney failure can occur within 1 to 2 weeks after the mushrooms are eaten, and people often need temporary hemodialysis (see Hemodialysis).

Gyromitra mushrooms also cause delayed vomiting and diarrhea and a low blood sugar level. Other problems include brain toxicity (such as seizures) and, after a few days, liver and kidney failure.

Most Cortinarius mushrooms originate in Europe. Vomiting and diarrhea may last for 3 days. Kidney failure, with symptoms of flank pain and a decreased amount of urine, may occur 3 to 20 days after the mushrooms are eaten. Kidney failure often resolves spontaneously.

Plant and Shrub Poisoning

A few commonly grown plants are poisonous. Highly toxic and potentially fatal plants include castor beans, jequirity beans, poison hemlock, and water hemlock, as well as oleander and foxglove, which contain digitalis glycosides. Few plant poisonings can be cured by specific antidotes.

Castor beans contain ricin, an extremely concentrated poison. Ricin has been used in assassination attempts. Castor bean seeds have a very tough shell so the bean must be chewed to release the poison. Jequirity beans contain abrin, a related and more potent toxin. They can cause death after swallowing. Children can die after chewing only one bean. Poisoning from castor beans or jequirity beans may cause severe vomiting and diarrhea (often bloody) after a delayed period. People later become delirious and have seizures. They may become comatose and die. Doctors sometimes try to flush the beans out of the stomach and intestines before they are absorbed.

Hemlock poisoning can cause symptoms within 15 minutes. People develop a dry mouth and later a rapid heart beat, tremors, sweating, seizures, and muscle weakness. Water hemlock may cause vomiting and diarrhea, delirium, seizures, and coma.

Oleander, foxglove, and the similar but less toxic lily of the valley, can cause vomiting and diarrhea, confusion, irregular heartbeat, and high levels of potassium in the bloodstream. These plants contain a substance very similar to the heart drug digoxin. Doctors sometimes treat people who are poisoned by these plants with a drug used to treat digoxin overdose.

Many other plants cause less serious toxic effects.

Moderately Poisonous Plants




Aloe and related plants

Gastroenteritis (see Gastroenteritis), kidney inflammation, and skin irritation

Supportive care* if the plant is swallowed and flushing (irrigation) with soap and water if the skin is irritated

Apricot, wild cherry, and peach pits and apple and other seeds (Prunus and Malus species), usually only if many seeds are chewed and swallowed

Symptoms of oxygen deprivation, such as nausea, dizziness, difficulty concentrating, headache, vomiting, drowsiness, and poor coordination (similar to those of carbon monoxide poisoning)

For serious poisoning, hydroxocobalamin given by vein and use of a cyanide antidote kit (including amyl nitrate given by inhalation and sodium nitrite and sodium thiosulfate given intravenously)

Aristolochia (also called birthworts or pipevines)

Formation of scar tissue in the kidneys

Supportive care*


Cholinergic symptoms

Supportive care* and atropine

Caladium (also called elephant ear or angel's wings) and related plants

Irritation of the mouth due to calcium oxalate crystals in the leaves

Supportive care* and use of milk or ice cream to help dissolve the irritant

Capsicum and related plants (peppers)

Irritation of the skin and mucous membranes

Supportive care* and flooding the affected area with water to wash the substance away (irrigation)

Colchicine (autumn crocus, meadow saffron, or glory lily)

Delayed gastroenteritis and malfunction (failure) of many organ systems

Interference with the bone marrow's ability to produce blood cells and platelets, possibly causing anemia, infection, and/or bleeding

Supportive care*

Deadly nightshade

Anticholinergic symptoms, a high body temperature, seizures, and hallucinations

Supportive care*

For a very high body temperature or seizures, possibly physostigmine

Dumbcane (dieffenbachia)

Damage to the mouth due to calcium oxalate crystals in the leaves

Supportive care* and use of milk or ice cream to help dissolve the crystals

Fava beans

In people with a deficiency of the enzyme G6PD (which protects red blood cells), gastroenteritis, fever, headache, and hemolytic anemia

Supportive care*

For severe anemia and poisoning, gradual removal and replacement of blood with equal volumes of fresh donor blood (exchange transfusion) considered

Green potatoes and potato sprouts

Gastroenteritis, hallucinations, and delirium

Supportive care*

Holly berries


Supportive care*


Anticholinergic symptoms, a high body temperature, seizures, and hallucinations

Supportive care*

For a very high body temperature or seizures, possibly physostigmine

Licorice (raw plant)

Too little potassium in the blood, high blood pressure, and swelling due to retention of fluid (edema)

Supportive care*

Lily of the valley

Too much potassium in blood and abnormal heart rhythms (arrhythmias)

Supportive care* and antibodies against digitalis



Supportive care*


A low heart rate, abnormal heart rhythms, numbness and tingling, and weakness

Supportive care*

Sometimes sodium bicarbonate given intravenously


Stinging and burning of the skin

Supportive care*

Nightshade, common or woody

Gastroenteritis, hallucinations, and delirium

Supportive care*

Nightshade, deadly

Anticholinergic symptoms, a high body temperature, seizures, and hallucinations

Supportive care*

For a very high body temperature or seizures, possibly physostigmine


Damage to the liver (when severe, causing jaundice, confusion, and a tendency to bleed)


Philodendron and related plants

Damage to the mouth due to calcium oxalate crystals in the leaves

Supportive care* and use of milk or ice cream to help dissolve the crystals


Mild irritation if it touches the mucous membranes of the mouth, nasal passages, vagina, or urethra


Poison ivy

Inflammation of the skin



Irritation if it touches the mucous membranes of the mouth, nasal passages, vagina, or urethra

Supportive care*


Damage to the mouth due to calcium oxalate crystals in the leaves

Supportive care* and use of milk or ice cream to help dissolve the crystals



Rarely, seizures, abnormal heart rhythms, and coma

Supportive care*

*Supportive care may include fluids given by vein (intravenously), treatments to maintain body functions (such as drugs to lower fever), drugs to increase blood pressure if it drops, and a ventilator.

Cholinergic symptoms include a slow heart rate, weakened contraction of the heart, dangerously low blood pressure, difficulty breathing (because airways are constricted), flushing, abdominal cramps, diarrhea, increased urination and salivation, watery eyes, increased sweating, and muscle cramping.

Anticholinergic symptoms include confusion, blurred vision, constipation, dry mouth, light-headedness, difficulty starting and continuing to urinate, and loss of bladder control.

G6PD = glucose-6-phosphate dehydrogenase.

Seafood Poisoning

Gastroenteritis may be caused by eating bony fish or shellfish. There are 3 common types of poisoning caused by eating bony fish—ciguatera, tetrodotoxin, and scombroid.

Ciguatera poisoning

This type of poisoning can occur after eating any of the more than 400 species of fish from the tropical reefs of Florida, the West Indies, or the Pacific. The toxin is produced by certain dinoflagellates, microscopic sea organisms that the fish eat. The toxin accumulates in their flesh. Larger, older fish are more toxic than smaller, younger ones. The flavor of the fish is not affected. Current processing procedures, including cooking, cannot destroy the toxin. The initial symptoms—abdominal cramps, nausea, vomiting, and diarrhea—may begin 2 to 8 hours after the person eats the fish and last 6 to 17 hours. Later symptoms may include itchiness, a pins-and-needles sensation, headache, muscle aches, a reversal of sensations of hot and cold, and facial pain. For months afterward, the sensations may be disabling. Doctors sometimes try to treat affected people with intravenous mannitol (a drug that reduces swelling and pressure), but it is unclear whether this provides any benefit. The toxin cannot be identified by any at-home test kit.

Tetrodotoxin poisoning

Symptoms caused by the toxin in the puffer fish (fugu, a sushi delicacy), which is found most commonly in the seas surrounding Japan, are similar to those caused by fish in ciguatera poisoning. If a large amount of the toxin is eaten, muscles can become paralyzed and death may result from paralysis of the muscles that regulate breathing. The toxin cannot be destroyed by cooking or freezing.

Scombroid poisoning

After fish such as mackerel, tuna, bonito, skipjack, and blue dolphin (mahi mahi) have been caught, the tissues of the fish break down, producing high levels of histamine. When ingested, histamine causes immediate facial flushing. It can also cause nausea, vomiting, stomach pain, and hives (urticaria) a few minutes after the fish is eaten. Symptoms, which are often mistaken for a seafood allergy, usually last less than 24 hours. The fish may taste peppery or bitter. Unlike other fish poisonings, this poisoning can be prevented by properly storing the fish after it is caught. Antihistamine drugs such as diphenhydramine and ranitidine may help.

Shellfish poisoning

Shellfish poisoning can occur from June to October, especially on the Pacific and New England coasts. Shellfish such as mussels, clams, oysters, and scallops may ingest certain poisonous dinoflagellates at certain times when the water has a red cast, called the red tide. The dinoflagellates produce a toxin that attacks nerves (such toxins are called neurotoxins). The toxin, saxitoxin, which causes paralytic shellfish poisoning, persists even after the food has been cooked. The first symptom, a pins-and-needles sensation around the mouth, begins 5 to 30 minutes after eating. Nausea, vomiting, and abdominal cramps develop next, followed by muscle weakness. Occasionally, the weakness progresses to paralysis of the arms and legs. Weakness of the muscles needed for breathing may even be severe enough to cause death. Those who survive usually recover completely.

Contaminant Poisoning

Gastroenteritis may affect people who have ingested unwashed fruits and vegetables sprayed with arsenic, lead, or organic insecticides; acidic fluids served in lead-glazed pottery; or food stored in cadmium-lined containers.


Most people with chemical food poisoning recover fully and rapidly with nothing more than replacement of fluids and electrolytes. As soon as symptoms begin, a person should try to consume large amounts of fluids. If fluids cannot be tolerated, the person needs to go to an emergency department for intravenous fluids.

If possible, it is often a good idea to rid the stomach of the toxic substance as quickly as possible. For most people, vomiting accomplishes this task. Saving a small amount of the first vomitus may be useful if tests are needed later. If a person cannot vomit adequately and symptoms are severe, a doctor may empty the stomach by placing a small tube through the nose or mouth into the stomach. A laxative helps to pass the toxins from the intestines more quickly.

Specific treatments are sometimes given when the toxin is known.

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