Food Poisoning - Causes

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What are the causes of food poisoning?

There many causes of food poisoning. Sometimes they classified by how quickly their symptoms begin after eating potentially contaminated food. Think of this as the incubation time from when food enters the body and symptoms begin. The following are several examples how this time classification can be arranged:

Short incubation or less than 16 to 24 hours

Chemical causes

  • Scombroid poisoning usually is due to poorly cooked or stored fish. The affected person will experience flushing, itching, shortness of breath, and difficulty swallowing within 1 to 2 hour of eating.
  • Ciguatera poisoning is another fish toxin that occurs after eating fish such as grouper, snapper, and barracuda. Symptoms include vomiting and diarrhea, muscle aches, and neurologic complaints including headache, numbness and tingling, hallucinations, and difficulty with balance (ataxia).
  • Mushroom ingestions can cause initial symptoms like vomiting and diarrhea. Eating Amanita mushrooms can cause liver and kidney failure leading to death.

Bacterium Causes

  • Staphylococcus aureus poisoning is due to a toxin that is pre-formed in food before it is eaten. It causes vomiting within 1 to 6 hours after eating the contaminated food.
  • Bacillus cereus is an infection that occurs after eating poorly cooked or raw rice.
  • Clostridium Perfringens is a spore that infects cooked meat that has been stored in an environment that was too warm. Within 8 to 12 hours, it may cause profuse diarrhea.

Intermediate incubation from about 1 to 3 days

Infections of the large intestine or colon can cause bloody, mucoid diarrhea associated with crampy abdominal pain.

  • Campylobacter, according to CDC data, is the number one cause of food borne disease in the United States.
  • Shigella spp contaminate food and water and cause dysentery (severe diarrhea often containing mucus and blood).
  • Salmonella infections often occur because of poorly or undercooked cooked, and poor handling of the chicken and eggs. In individuals with weakened immune systems, including the elderly, the infection can enter the bloodstream and cause potentially life-threatening infections.
  • Vibrio parahaemolyticus can contaminate saltwater shellfish and cause a watery diarrhea.

Diarrhea due to small bowel infection tends not to be bloody, but infections may affect both the small and large intestine at the same time.

  • E. coli (enterotoxigenic) is the most common cause of traveler's diarrhea. It lacks symptoms such as fever or bloody diarrhea.
  • Vibrio cholerae, often from contaminated drinking, water produces a voluminous watery diarrhea resembling rice-water.
  • Viruses like Norwalk, rotavirus and adenovirus tend to have other symptoms associated with an infection including fever, chills, headache, and vomiting.
  • Botulism is caused by Clostridium botulinum toxin and may present with fever, vomiting, mild diarrhea, numbness, and weakness leading to paralysis.

Long incubation 3 to 5 days

  • Hemorrhagic E. coli (mainly E. coli 0157:H7) can cause inflammation of the colon leading to bloody stools. In some children, about a week after infection, it can progress to hemolytic uremic syndrome (HUS). Elderly individuals may contract thrombotic thrombocytopenic purpura (TTP). Toxins from the bacteria enter the blood stream and hemolyze or destroy red blood cells (hemo=blood + lyse=disintegrate). In addition, the toxins cause kidney failure and uremia, where waste products build up in the body.
  • Yersinia enterocolitica may cause inflammation of lymph nodes in the lining of the abdomen and may mimic appendicitis.

Very long incubation up to a month


  • Giardiasis may occur after drinking water from lakes or rivers that have been contaminated by beavers, muskrats, or sheep that have been grazing. It also can be passed from person to person, for example in day care settings.
  • Amoebiasis is encountered in contaminated drinking water, usually in tropical or semitropical climates and can be passed person to person.
  • Trichinosis is due to an infection from eating undercooked pork or wild game such as bear meat. Aside from fever and gastrointestinal complaints, symptoms include muscle pain, facial swelling, and bleeding around the eyes and under the fingernails.
  • Cysticercosis is often seen in developing countries where water is contaminated with pork tapeworms and the person drinks the ova form the tapeworm. The infection can invade the brain (neurocysticercosis) causing seizures.


  • Listeriosis usually occurs after foods contaminated with Listeria bacteria are ingested. These include unpastruized, raw milk, soft cheeses, and processed meats and poultry. Vegetables and fruits may also become infected with Listeria. The bacteria may lay dormant in or on the surface of the food products for weeks.
  • Brucellosis occurs by ingesting raw or unpasteurized milk and cheese, especially goat's milk contaminated with Brucella spp


  • Hepatitis A is spread by poor food handling, and not due to blood exposure such as hepatitis B and C.


  • Toxoplasmosis is usually transmitted to humans from cat feces containing Toxoplasma parasites; most infections are asymptomatic, but people who are immune depressed can develop systemic disease symptoms.


  • Bovine Spongiform encephalopathy (mad cow disease) is acquired by eating foods containing prions (transmissible agents that induces abnormal folding of brain protein) contaminating brain or spinal cord from infected cows.
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See what others are saying

Comment from: Linda, 45-54 Female (Patient) Published: August 12

I ate pre-packed fruit salad from a nationwide pharmacy chain that also sells food.

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Comment from: Matt, 35-44 Male (Patient) Published: April 22

On Friday my fiance and I ordered pizza for delivery, the evening before our bridal shower. We ate it at 10 p.m. and both woke at 3 a.m. and proceeded to vomit and have diarrhea until Sunday morning around 9.

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