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Food Poisoning

What Is Food Poisoning?

Food poisoning refers to illness brought on by ingesting foods contaminated with living micro-organisms, toxins produced by microorganisms, poisonous chemicals, or poisonous fish, shellfish, or plants (such as mushrooms). The digestive tract is most commonly affected. However, botulism, a life- threatening form of food poisoning, primarily affects the nervous system and may cause respiratory failure.

Food poisoning may result from improper storage and handling of food, such as inadequate refrigeration or touching food with soiled hands or machinery. Symptoms generally develop within one to 48 hours after eating. Some types of food poisoning (notably cholera and shigellosis) may take from three to five days to produce symptoms.

Food poisoning is suspected when sudden, acute gastrointestinal symptoms arise. It is difficult to prove that food poisoning is the cause of illness unless several people develop symptoms after sharing the same foods or after eating in the same restaurant..

The illness often subsides spontaneously after one to five days; however, severe or persistent symptoms require treatment and sometimes hospitalization.

Who Gets Food Poisoning?

When people come down with a “bug” accompanied by symptoms such as headache and stomach distress, it’s often dismissed as “stomach flu” or “24-hour virus”—but it may be food poisoning. And some types of microbes can cause severe illness that can be fatal in the elderly, in children, in people with certain disorders (such as diabetes), and in people whose immune systems are depressed, such as cancer patients. In addition, foodborne illnesses can also cause serious health problems during pregnancy—both for the expectant mother and her unborn baby.

The Centers for Disease Control and Prevention (CDC) estimates that 76 million cases of food poisoning occur each year. Most go unreported since they are mild and last for only a day or two. But more than 300,000 cases are serious enough to require hospitalization, and an estimated 5,000 deaths each year are related to foodborne infections.


The onset of symptoms can occur anywhere from one hour to seven days after eating contaminated food, depending on the infectious agent. Symptoms of food poisoning include:

  • Diarrhea
  • Abdominal pain and cramps
  • Nausea and vomiting
  • Fever
  • Headaches
  • Weakness and fatigue
  • Bloody stool

Causes/Risk Factors

  • Food poisoning is primarily caused by bacteria and some viruses—typically when food is improperly handled and prepared or kept at room temperature (rather than being refrigerated) for long periods. The bacterium Salmonella is by far the most frequent cause of foodborne illness, and it is rapidly becoming more prevalent. Other common bacteria that cause gastroenteritis include Campylobacter, Shigella, and Yersinia.
  • Each year an estimated 25,000 cases of food poisoning are attributed to E. coli 0157:H7, a particularly dangerous strain of E. coli—a bacteria widely present in fecal matter—that can spread to humans when they consume food or water contaminated with microscopic amounts of cow feces. Most cases are associated with undercooked, contaminated ground beef. Some new types of E. coli have been described in the last few years. These bacteria can cause kidney problems in addition to gastrointestinal symptoms.
  • Fish and shellfish are another common source of food poisoning, especially when they are eaten raw.
  • Many species of wild mushrooms and toadstools contain non-infectious toxins that can cause headache, nausea, vomiting, diarrhea, blurred vision, and other symptoms.

What If You Do Nothing?

Most cases of food poisoning are not serious and recovery usually occurs within three days without any medical care. However, the disease can be fatal if the treatment of a serious food poisoning case is delayed. Symptoms to be concerned about include the following:

  • bloody diarrhea or pus in the stool (possible Campylobacter or Shigella infection).
  • headache, stiff neck, and fever (possible Listeria monocytogenes infection).
  • rapid heart rate or dizziness after standing up suddenly, when accompanied by vomiting, nausea, or diarrhea (possible dehydration).
  • tingling in the arms and legs, sometimes around the mouth, blurred vision, weakness, or numbness (possible botulism poisoning).


  • Vomit, feces, or blood may be cultured or tested.
  • If available, samples of suspected foods are examined for contaminants.


  • Diarrhea may help rid the body of bacteria and toxins. For that reason, check with your doctor before taking antidiarrheal medications.

  • Avoid eating solid food until the diarrhea has passed.

  • Drink plenty of fluids to prevent dehydration from diarrhea.

  • A drink containing electrolytes and sugar may be needed to replace minerals lost with severe diarrhea.

  • Intravenous fluids may be needed to treat severe dehydration.

  • Medication to prevent vomiting (antiemetics) may be prescribed in severe cases, although vomiting may help rid the body of toxins.

  • Antibiotics may be prescribed in some cases, if certain infectious agents are involved.


  • Wash your hands thoroughly with warm water and soap before preparing food.

  • Make sure food is handled, cleaned, cooked, and refrigerated properly.

  • Don’t buy or use food in cans that are rusty, bulging, dented, or leaking.

  • Avoid tasting food to check for contamination.

  • Don’t eat mushrooms you have picked.

  • Don’t consume unpasteurized dairy products.

  • Throw away any questionable leftovers.

  • If you can your own fruits and vegetables at home, follow guidelines about safe procedures to protect against botulism.

When To Call Your Doctor

  • The elderly, young children, and anyone with a weakened immune system (such as those diagnosed with AIDS or undergoing treatment for cancer) should be taken to a doctor immediately if they develop even mild symptoms of food poisoning. These people are at greater risk of life-threatening complications.

  • Call a doctor if you develop any of the following: sudden, severe or bloody diarrhea; a fever over 102˚F; severe abdominal pain.

  • Call a doctor if food poisoning symptoms do not subside within a week.

Reviewed by Jenifer K. Lehrer, M.D., Department of Gastroenterology, Aria-Torresdale Hospital, Aria Health System, Philadelphia, PA. Review provided by VeriMed Healthcare Network.