Food poisoning occurs when you swallow food or water that has been contaminated with certain types of bacteria, parasites, viruses, or toxins.
Most cases of food poisoning are due to common bacteria such as Staphylococcus or Escherichia coli (E. coli).
Food poisoning more commonly occurs after eating at picnics, school cafeterias, large social functions, or restaurants. One or more people may become sick.
Food poisoning is caused by certain bacteria, viruses, parasites, or toxins. Types of food poisoning include:
Bacteria may get into your food in different ways:
- Meat or poultry may come into contact with intestinal bacteria when being processed
- Water that is used during growing or shipping may contain animal or human waste
- Improper food handling or preparation
Food poisoning often occurs from eating or drinking:
- Any food prepared by someone who did not wash their hands properly
- Any food prepared using unclean cooking utensils, cutting boards, or other tools
- 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 properly
- Raw fish or oysters
- Raw fruits or vegetables that have not been washed well
- Raw vegetable or fruit juices and dairy
- Undercooked meats or eggs
- Water from a well or stream, or city or town water that has not been treated
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 there is more exposure to germs that cause food poisoning
Pregnant and breastfeeding women have to be especially careful to avoid food poisoning.
When you develop symptoms depends on the exact cause of the food poisoning. The most common types of food poisoning generally cause symptoms within 2 - 6 hours of eating the food.
Possible symptoms include:
Exams and Tests
Your health care provider will examine you for signs of food poisoning, such as pain in the stomach and signs your body does not have as much water and fluids as it should. This is called dehydration.
You will be asked about the foods you have eaten recently.
Tests may be done on your blood, stools, vomit, or the food you have eaten to determine the cause of your symptoms. However, tests may not be able to prove that you have food poisoning.
In rare but possibly serious cases, your health care provider may order a sigmoidoscopy, a procedure in which a thin tube placed in the anus to look for the source of bleeding or infection.
You will usually recover from the most common types of food poisoning within a couple of days. The goal is to make you feel better and make sure your body maintains the proper amount of fluids.
- Don't eat solid foods until the diarrhea has passed, and avoid dairy products, which can worsen diarrhea (due to a temporary state of lactose intolerance).
- Drink any fluid (except milk or caffeinated beverages) to replace fluids lost by diarrhea and vomiting.
- Give children an electrolyte solution sold in drugstores.
If you have diarrhea and are unable to drink fluids (for example, due to nausea or vomiting), you may need medical attention and fluids given through a vein (by IV). This is especially true for young children.
If you take diuretics, you need to manage diarrhea carefully. Talk to your health care provider -- you may need to stop taking the diuretic while you have the diarrhea. Never stop or change medications without talking to your health care provider and getting specific instructions.
For the most common causes of food poisoning, your doctor would 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 or a fever. Do not give these medicines to children.
If you have eaten toxins from mushrooms or shellfish, you will need medical attention right away. The emergency room doctor will take steps to empty out your stomach and remove the toxin.
Most people fully recover from the most common types of food poisoning within 12 - 48 hours. Serious complications can arise, however, from certain types of food poisoning.
Death from food poisoning in people who are otherwise healthy is rare in United States.
Dehydration is the most common complication. This can occur from any of the causes of food poisoning.
Less common but much more serious complications depend on the bacteria that is causing the food poisoning. These may include arthritis, bleeding problems, kidney problems, damage to the nervous system, and swelling or irritation in the tissue around the heart.
When to Contact a Medical Professional
Call for an appointment with your health care provider if you have:
- Blood or pus in your stools
- Black stools
- Stomach pain that does not go away after a bowel movement
- Symptoms of dehydration (thirst, dizziness, light-headedness)
- Diarrhea with a fever above 101°F (100.4°F in children)
- Recently traveled to a foreign country and developed diarrhea
Also call your doctor if:
- The diarrhea gets worse or does not get better in 2 days for an infant or child, or 5 days for adults
- A child over 3 months old has been vomiting for more than 12 hours; in younger babies, call as soon as vomiting or diarrhea begins
Go to the emergency room or call your local emergency number, such as 911, if:
- Bleeding is excessive or your stools are maroon or black
- You may have poisoning from mushrooms, fish, or botulism
- Your heart is racing, pounding, or skipping
See: Preventing 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.
Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; George F. Longstreth, MD, Department of Gastroenterology, Kaiser Permanente Medical Care Program, San Diego, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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