Food poisoning occurs when you swallow food or water that contains bacteria, parasites, viruses, or toxins made by these germs. Most cases are caused by common bacteria such as Staphylococcus or E. coli.
Causes, incidence, and risk factors
Food poisoning can affect one person or a group of people who all ate the same contaminated food. It is more common happens after eating at picnics, school cafeterias, large social functions, or restaurants.
The germs may get into the food you eat (called contamination) in different ways:
Meat or poultry can come into contact with bacteria from the intestines of an animal that is being processed.
Water that is used during growing or shipping can contain animal or human waste.
Food may be handled in an unsafe way during preparation in grocery stores, restaurants, or homes.
Food poisoning can occur after eating or drinking:
Any food prepared by someone who does not wash their hands properly
Any food prepared using cooking utensils, cutting boards, and other tools that are not fully cleaned
Dairy products or food containing mayonnaise (such as coleslaw or potato salad) that have been out of the refrigerator too long
Frozen or refrigerated foods that are not stored at the proper temperature or are not reheated the right amount
Raw fish or oysters
Raw fruits or vegetables that have not been washed well
Raw vegetables or fruit juices and dairy products (look for the word "pasteurized," which means the food has been treated to prevent contamination)
Undercooked meats or eggs
Water from a well or stream, or city or town water that has not been treated
Many types of germs may cause food poisoning, including:
E. coli enteritis
Infants and elderly people are at the greatest risk for food poisoning. You are also at higher risk if:
You have a serious medical condition, such as kidney disease or diabetes.
You have a weakened immune system.
You travel outside of the United States to areas where you are exposed to germs that cause food poisoning.
Pregnant and breastfeeding women should use extra care to avoid food poisoning.
Symptoms from the most common types of food poisoning usually start within 2 - 6 hours of eating the food. That time may be longer or shorter, depending on the cause of the food poisoning.
Sodha SV, Griffin PM, Hughes JM. Foodborne disease. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 99.
Craig SA, Zich DK. Gastroenteritis. In: Marx JA, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, Pa: Mosby Elsevier;2009:chap 92.
George F. Longstreth, MD, Department of Gastroenterology, Kaiser Permanente Medical Care Program, San Diego, California. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.