Food poisoning

Food poisoning is the result of eating organisms or toxins in contaminated food. Most cases of food poisoning are from common bacteria like Staphylococcus or E. coli.

Causes, incidence, and risk factors

Food poisoning can affect one person or it can occur as an outbreak in a group of people who all ate the same contaminated food.

Even though food poisoning is relatively rare in the United States, it affects between 60 and 80 million people worldwide each year and results in approximately 6 to 8 million deaths.

Food poisoning tends to occur at picnics, school cafeterias, and large social functions. These are situations where food may be left unrefrigerated too long or food preparation techniques are not clean. Food poisoning often occurs from undercooked meats or dairy products (like mayonnaise mixed in coleslaw or potato salad) that have sat out too long.

Food poisoning can be caused by:

  • Staph aureus  
  • E. coli enteritis  
  • Salmonella  
  • Shigella  
  • Campylobacter  
  • Cholera  
  • Botulism  
  • Mushroom poisoning  
  • Listeria  
  • Bacillus cereus  
  • Fish poisoning  
  • Yersinia

Infants and elderly people have the greatest risk for food poisoning. You are also at higher risk if you have a serious medical condition, like kidney disease or diabetes, a weakened immune system, or you travel outside of the U.S. to areas where there is more exposure to organisms that cause food poisoning. Pregnant and breastfeeding women have to be especially careful.


The symptoms from the most common types of food poisoning generally start within 2 to 6 hours of eating the food responsible. That time may be longer (even a number of days) or shorter, depending on the toxin or organism responsible for the food poisoning. The possible symptoms include:

  • Nausea and vomiting  
  • Abdominal cramps  
  • Diarrhea (may be bloody)  
  • Fever and chills  
  • Weakness (may be serious and lead to respiratory arrest, as in the case of botulism)  
  • Headache

Botulism is a very serious form of food poisoning that can be fatal. It can come from improper home canning

Signs and tests
Your healthcare provider will examine you for signs and symptoms of food poisoning, such as stomach problems and dehydration. Your provider will also ask about foods you have eaten recently. Tests of your vomit, blood, stool, and any leftover food may identify the cause. Even if you have food poisoning, however, these tests may not be able to verify it.

In rare but possibly serious cases, your doctor may order one or more of the following procedures:

  • Sigmoidoscopy (putting a thin, tube-like tool into the anus) to look for the source of bleeding or infection if these symptoms do not go away and the cause has not been found.  
  • Electromyography (a test to measure electric impulses in the muscles) to check for botulism.  
  • Lumbar puncture (a test of fluid from the spine) if you have signs of a nervous system disorder.


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 avoid dehydration. Drink any fluid (except milk or caffeinated beverages) to replace fluids lost by diarrhea and vomiting. Children should be given an electrolyte sold in drugstores. Don’t eat solid foods until the diarrhea has passed, and avoid dairy, which can worsen diarrhea.

If you have diarrhea and are unable to drink fluids (for example, due to nausea or vomiting), you may need medical attention and intravenous fluids. This is especially true for young children. If you take diuretics, you need to manage diarrhea carefully. Talk to your doctor - you may need to stop taking the diuretic while you have the diarrhea. Medications should NEVER be stopped or changed without discussing with your doctor and getting specific instructions.

For the most common causes of food poisoning, your doctor would NOT prescribe antibiotics. Antibiotics can actually prolong diarrhea and keep the organism in your body longer.

If you have eaten toxins from mushrooms or shellfish, you will need to be seen right away. The emergency room doctor will take steps to empty out your stomach and remove the toxin.

Expectations (prognosis)
Full recovery from the most common types of food poisoning usually occurs within 12 and 48 hours. Serious complications can arise, however, from certain types of food poisoning.


Dehydration is the most common complication. This can occur from any of the causes of food poisoning.

Less common but much more serious complications include:

  • Respiratory distress, including the need for support on a breathing machine (botulism)  
  • Kidney problems (Shigella, E. coli)  
  • Bleeding disorders (E. coli and others)  
  • Arthritis (Yersinia and Salmonella)  
  • Nervous system disorders (Botulism, Campylobacter)  
  • Pericarditis (Salmonella)  
  • Death - 50% of people with mushroom or certain fish poisonings (like puffer fish) die and 10% with botulism

Calling your health care provider

Call your doctor if:

  • You have diarrhea and are unable to drink fluids due to nausea or vomiting.  
  • You are on diuretics and have diarrhea, nausea, or vomiting.  
  • Diarrhea lasts for more than 2 to 3 days.  
  • There is blood in your stools.  
  • You have a fever over 101°F.

Call 911 if:

  • You have signs of dehydration (thirsty, dizzy, lightheaded, faint).  
  • Bleeding is excessive or your stools are maroon or black.  
  • You are short of breath or having trouble breathing.  
  • Your heart is racing, pounding, or skipping.  
  • You may have poisoning from mushrooms, fish, or botulism.  
  • You have any nervous system symptoms like weakness, double vision, difficulty speaking, or paralysis.  
  • You have trouble swallowing.

To prevent food poisoning, take the following steps when preparing food:

  • Carefully wash your hands and clean dishes and utensils.  
  • Use a thermometer when cooking. Cook beef to at least 160°F, poultry to at least 180°F, and fish to at least 140°F.  
  • DO NOT place cooked meat or fish back onto the same plate or container that held the raw meat, unless the container has been thoroughly washed.  
  • Promptly refrigerate any food you will not be eating right away. Keep the refrigerator set to around 40°F and your freezer at or below 0°F. DO NOT eat meat, poultry, or fish that has been refrigerated uncooked for longer than 1 to 2 days.  
  • DO NOT use outdated foods, packaged food with a broken seal, or cans that are bulging or have a dent.  
  • DO NOT use foods that have an unusual odor or a spoiled taste.

Other steps to take:

  • If you take care of young children, wash your hands often and dispose of diapers carefully so that bacteria can’t spread to other surfaces or people.  
  • If you make canned food at home, be sure to follow proper canning techniques to prevent botulism.  
  • DO NOT feed honey to children under 1 year of age.  
  • DO NOT eat wild mushrooms.  
  • When traveling where contamination is more likely, eat only hot, freshly cooked food. Drink water only if it’s been boiled. DO NOT eat raw vegetables or unpeeled fruit.  
  • DO NOT eat shellfish exposed to red tides.  
  • If you are pregnant or have a weakened immune system, DO NOT eat soft cheeses, especially imported from countries outside the U.S.

If other people may have eaten the food that made you sick, let them know. If you think the food was contaminated when you bought it from a store or restaurant, tell the store and your local health department.

Johns Hopkins patient information

Last revised: December 4, 2012
by Harutyun Medina, M.D.

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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.