Food Poisoning


What Is It?

Most commonly, food poisoning results from a reaction to food or water contaminated during improper cooking, handling or storage. The most common contaminants are bacterial, especially salmonella. Other contaminants include viruses, parasites and toxins. Food poisoning usually leads to severe gastrointestinal distress, which is accompanied by abdominal cramping, vomiting and diarrhea.

Food poisoning, although common, often can be prevented easily. An estimated 85 percent of food-poisoning incidents can be prevented by handling and preparing food properly. Usually, food poisoning goes away within a day or two. However, in some cases, food poisoning is quite dangerous. In the United States, food poisoning results in more than 300,000 hospitalizations each year and causes 5000 deaths.


Symptoms of food poisoning include:

  • Nausea
  • General weakness or exhaustion
  • Headache
  • Abdominal pain and cramps
  • Abrupt vomiting and diarrhea


Because food poisoning usually goes away once the contaminant or toxin has passed through the body, doctors cannot always determine the exact cause of symptoms. If symptoms continue for more than 48 hours, it may be necessary to examine a stool sample under a microscope. Your doctor also may want to take a sample from blood, stools or the food in question. 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 percent of food poisoning is related to consuming 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 an hour suggests a toxin was involved
  • Several hours or more suggests a bacterial infection
  • More than 12 hours suggests a viral infection

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.

Once you have selected safe foods, be certain to store them 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 stored at an improper temperature and food handlers who have poor personal hygiene most commonly are found during commercial and institutional food preparation. 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
  • Elderly persons

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 high fever


For most people, food poisoning is an unpleasant experience that lasts for a day or two, then it 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.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.