Chemical food poisoning results from eating a plant or animal that contains a toxin.
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, 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 prescribe a sedative (such as lorazepam).
In poisoning caused by many species of Inocybe and some species of Clitocybe, the dangerous substance is muscarine. Symptoms, which begin a few minutes to 2 hours after eating, may include increased tearing and salivation, narrowing (constriction) of the pupils, sweating, vomiting, stomach cramps, diarrhea, dizziness, confusion, coma, and, occasionally, seizures. Symptoms are usually mild and go away within 12 hours. Doctors give atropine 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 24 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 reduce or stop urination. 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. Those with liver failure may survive if given a liver transplant.
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. Symptoms of gastroenteritis may last for 3 days. Kidney failure, with symptoms of flank pain and decreased urine output, may occur 3 to 20 days after ingestion. 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 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.
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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.
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 and that accumulate 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.
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. Death may result from paralysis of the muscles that regulate breathing. The toxin cannot be destroyed by cooking or freezing.
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 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.
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.
Last full review/revision September 2007 by Thomas G. Boyce, MD, MPH