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.
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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.
Possible symptoms include:
Signs and tests
Your health care provider will look for signs of food poisoning. These may include pain in the stomach and signs your body does not have as much water and fluids as it should (dehydration).
Tests may be done on your stools or the food you have eaten to find out what type of germ is causing your symptoms. However, tests may not always find the cause of the diarrhea.
In more serious cases, your health care provider may order a sigmoidoscopy. A thin, hollow tube with a light on the end is placed in the anus to look for the source of bleeding or infection.
Most of the time, you will recover in a couple of days. The goal is to make you feel better and make sure your body has the proper amount of fluids.
Getting enough fluids and learning what to eat will help keep you or your child comfortable. You may need to:
You can drink oral rehydration mixtures to replace fluids and minerals lost through vomiting and diarrhea.
Oral rehydration powder can be purchased from a pharmacy. Be sure to mix the powder in safe water.
You can make your own mixture by dissolving ½ teaspoonful each salt and baking soda and 4 tablespoonsful sugar in 4 ¼ cups (1 liter) water.
If you have diarrhea and are unable to drink or keep down fluids, you may need fluids given through a vein (by IV). This is may be more common in young children.
If you take diuretics, ask your health care provider if you need to stop taking the diuretic while you have diarrhea. Never stop or change medicines before talking to your doctor.
For the most common causes of food poisoning, your doctor will NOT prescribe antibiotics.
You can buy medicines at the drugstore that help slow diarrhea.
Do not use these medicines without talking to your health care provider if you have bloody diarrhea, a fever, or the diarrhea is severe.
Do not give these medicines to children.
Most people fully recover from the most common types of food poisoning within 12 - 48 hours. Some types of food poisoning can cause serious complications.
Death from food poisoning in people who are otherwise healthy is rare in the United States.
Dehydration is the most common complication. This can occur from any causes of food poisoning.
Less common, but much more serious complications depend on the bacteria that are causing the food poisoning. These may include:
Calling your health care provider
Call for an appointment with your health care provider if you have:
- Blood or pus in your stools
- Diarrhea and are unable to drink fluids due to nausea or vomiting
- A fever above 101°F, or your child has a fever above 100.4°F along with diarrhea
- Signs of dehydration (thirst, dizziness, light-headedness)
- Recently traveled to a foreign country and developed diarrhea
- Diarrhea that has not gotten better in 5 days (2 days for an infant or child), or has gotten worse
- A child who has been vomiting for more than 12 hours (in a newborn under 3 months you should call as soon as vomiting or diarrhea begins)
- Food posoning from mushrooms, fish, or botulism
Schiller LR, Sellin JH. Diarrhea. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2010:chap 15.
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.