Food poisoning is an illness caused by eating contaminated food. Infectious organisms (bacteria, viruses, parasites) or their toxins are the most common causes of food poisoning.

Infectious organisms or their toxins can contaminate food at any point of processing or production. Contamination may also occur at home if the food is improperly handled or cooked.

In general, food poisoning is mild and resolves without treatment. However, severe food poisoning may require medical attention.



The symptoms of food poisoning vary relative to the source of contamination. Most types of food poisoning cause one or more of the following symptoms:


  • Nausea
  • Vomiting
  • Abdominal pain and cramps
  • Watery diarrhea
  • Fever


The symptoms may start within hours of eating the contaminated food or they may start days or even weeks later. Sickness brought on by food poisoning typically lasts from a few hours to several days.



Food contamination can occur at any point during its production: growing, harvesting, processing, storing, shipping or preparing. Cross-contamination (transfer of harmful organisms from one surface to another) is often the cause of food contamination.

Bacterial, viral or parasitic agents can cause food poisoning. The following are some of the possible contaminants:


  • Campylobacter: mostly in meat and poultry but also contaminated water and unpasteurized milk.
  • Clostridium botulinum: home-canned foods with low acidity
  • Clostridium perfringens: meats, stews and gravies
  • Escherichia coli: contaminated beef or unpasteurized milk, apple cider and contaminated water
  • Giardia lamblia: raw, ready-to-eat products and contaminated water
  • Hepatitis A: raw, ready-to-eat products and shellfish from contaminated water
  • Listeria: hot dogs, luncheon meats, unpasteurized milk and cheeses
  • Noroviruses: raw, ready-to-eat products and shellfish from contaminated water
  • Rotavirus: raw, ready-to-eat products
  • Salmonella: raw or contaminated meat, poultry, milk or egg yolks
  • Shigella: seafood and raw, ready-to-eat products
  • Staphylococcus aureus: meats and prepared salads, cream sauces and cream-filled pastries
  • Vibrio vulnificus: raw oysters and raw or undercooked mussels, clams and whole scallops


Risk factors

Developing food poisoning after ingesting contaminated food depends on the organism, the amount of exposure, age and overall health.


Risk factors include:


  • Increasing age: increasing age weakens the immune system and slows its response to infectious organisms.
  • Pregnancy: changes in metabolism and circulation may increase the risk of food poisoning. The reaction may be more severe during pregnancy.
  • Chronic disease: diabetes, liver disease, AIDS or receiving chemotherapy or radiation therapy reduces the immune response.
  • Underdeveloped immune system: in infants and children.



The most common complication of food poisoning is dehydration. Healthy adults should be able to counter the dehydration with enough fluids.

Infants, older adults and people with suppressed immune systems or chronic diseases may become severely dehydrated. In such cases, hospitalization may be necessary to receive intravenous fluids. In extreme cases, dehydration can be fatal.


Some types of food poisoning can lead to serious complications for certain people. These include:


  • Listeria monocytogenes: complications of listeria poisoning may be most severe for an unborn baby. In early pregnancy a listeria infection may cause a miscarriage. In later pregnancy, a listeria infection may lead to stillbirth, premature birth or a potentially fatal infection in the baby after birth.
  • Escherichia coli: certain strains of E. coli can cause a complication known as hemolytic uremic syndrome. This syndrome damages the lining of the tiny blood vessels in the kidneys and in some cases it may lead to kidney failure.



To prevent food poisoning at home:


  • Wash hands, utensils and food surfaces often
  • Separate raw foods from ready-to-eat foods
  • Cook foods to a safe temperature
  • Refrigerate or freeze perishable foods promptly
  • Defrost food safely
  • Throw food out when in doubt