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Food poisoning

Medically reviewed by Last updated on Aug 10, 2023.

What is Food poisoning?

Harvard Health Publishing

Most commonly, food poisoning is a reaction to food or water contaminated during improper cooking, handling or storage. The most common contaminants are bacteria, such as salmonella, Campylobacter and E. coli. Other contaminants include viruses, parasites and toxins. Food poisoning usually leads to abdominal cramping, vomiting and diarrhea.

Food poisoning, although common, often can be prevented easily. An estimated 85% of food-poisoning incidents can be prevented by handling and preparing food properly. Usually, symptoms subside within a day or two. However, in some cases, food poisoning is quite dangerous.


Symptoms of food poisoning include:

  • Nausea and vomiting
  • General weakness
  • Abdominal pain/cramping
  • Diarrhea
  • Fever.


The diagnosis is usually made on the basis of symptoms alone, and fortified if there is an accompanying history of a person eating with you who also became sick. If a doctor wants to pinpoint the microorganism that caused the food poisoning, you will be asked to provide a stool sample to be examined in a laboratory. Your doctor also may want to take a sample of your blood for testing. If you have some of the food that might have made you sick, ask your doctor if it is important to test for infectious organisms or a toxin. The sample can be cultured in a laboratory, which means it is placed on a special material that encourages organisms that may be in the sample to grow, so they can be identified.

Up to 80% of food poisoning is related to eating commercially prepared foods or institutional foods. In such cases, questioning others who have eaten the same foods may help to determine the cause.

Information about the length of time between eating the food and the beginning of symptoms can help in diagnosing the problem:

  • Less than six hours suggests that the infection was caused by a type of bacterium that creates a toxin in the food before it was eaten (such as staphylococcus)
  • Twelve hours or more suggests the infection was caused by a type of bacterium that makes a toxin after the food is eaten (such as certain types of E. coli), or a bacterium, virus or parasite that can damage the cells lining the intestine (such as salmonella).

Expected duration

In general, food poisoning goes away in one to three days, although some types of food poisoning may last much longer.


To prevent food poisoning, select safe foods. Take the following steps:

  • Examine foods carefully. Buy foods before their expiration date, make certain that cans of food are not dented or bulging, and make sure that jars of food are sealed tightly.
  • Be particularly cautious when buying shellfish, dairy products and eggs.
  • Buy foods only from reliable sources. Avoid street vendors and roadside markets.
  • Avoid foods that contain raw eggs, such as mayonnaise.
  • Do not eat mushrooms, including wild ones, unless sold by a reliable source.

Store foods properly:

  • Refrigerate or freeze perishables immediately.
  • Check your refrigerator and freezer periodically to ensure that they operate at proper temperatures (41 degrees Fahrenheit, 0 degrees Fahrenheit for the freezer).
  • Store items according to their labeled instructions.
  • Thaw food in the refrigerator. Leaving food to thaw at room temperature gives bacteria a chance to grow.
  • Store nonperishable items in a cool, dry place.

Prepare foods safely:

  • Keep utensils and cooking surfaces clean.
  • Always wash your hands before and after preparing food, and rinse fruits and vegetables thoroughly.
  • Use a cutting board that is smooth, hard and nonporous and clean it with soap and hot water before and after each use.
  • Each week, sterilize dishcloths and sponges in hot water and sanitize the sink and drain with a cleaning solution.
  • Make sure all food is cooked thoroughly and be particularly cautious with seafood and poultry.
  • Use a meat thermometer to make sure that food is cooked thoroughly.
  • Serve foods immediately after cooking.

Be aware that food served in restaurants or institutions may not have been stored at the proper temperature, and that food handlers may not have the best personal hygiene. When eating at a restaurant, order cautiously. Be wary of soft cheeses, raw seafood and anything that contains raw eggs.

Food irradiation is another effective means to prevent food poisoning. During irradiation, foods are exposed briefly to a radiant energy source, such as gamma rays or electron beams, within a shielded facility. Irradiation is not a substitute for properly manufacturing and handling food. The process, however, can kill harmful bacteria and greatly reduce potential hazards, especially when used to treat meat and dairy products. Irradiation is a controversial practice and is not well accepted in some areas of the world. Irradiated foods are not widely available in the United States.


Because large amounts of fluids are lost through vomiting and diarrhea, treatment of food poisoning focuses on preventing dehydration. If you have food poisoning, you must drink fluids, even if you have trouble keeping them down.

Once you can tolerate fluids without vomiting, you can begin to add bland foods to your diet. If vomiting or diarrhea persists for more than 24 hours, a doctor may prescribe medications to suppress nausea, and may provide fluids intravenously. For some infectious causes of food poisoning, antibiotics may be recommended. People with very severe food poisoning may need to be admitted to a hospital.

When to call a professional

Call a doctor immediately if food poisoning is suspected in:

  • People with an impaired immune system
  • Pregnant women
  • Young children
  • The elderly.

If you are otherwise healthy, you should call a doctor if:

  • Vomiting and nausea last more than 24 hours
  • Vomiting and nausea are severe and abrupt and are accompanied by a feeling of extreme weakness
  • Any of the symptoms of food poisoning are accompanied by fever exceeding 102 degrees Fahrenheit
  • Diarrhea is severe or contains blood.


For most people, food poisoning is an unpleasant experience that lasts for a day or two, then passes. In very young children, elderly people, people with compromised immune systems and pregnant women, it can be dangerous. Anyone in these risk groups should go to an emergency room immediately.

Additional info

American College of Gastroenterology (ACG)

American Gastroenterological Association

Center for Food Safety & Applied Nutrition

Food Safety and Inspection Service

U.S. Food and Drug Administration (FDA)

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.