Food Poisoning

Medically Reviewed on 7/12/2023

What is food poisoning?

Food poisoning commonly causes stomach cramps.
Food poisoning commonly causes stomach cramps.

Food poisoning is a foodborne disease. Ingestion of food that contains a toxin, chemical, or infectious agent (like a bacterium, virus, parasite, or prion) may cause adverse symptoms in the body. Those symptoms may be related only to the gastrointestinal tract causing vomiting or diarrhea or they may involve other organs such as the kidney, brain, or muscle.

Typically most foodborne diseases cause vomiting and diarrhea that tend to be short-lived and resolve on their own, but dehydration and electrolyte abnormalities may develop. The Centers for Disease Control and Prevention (CDC) estimates approximately 48 million people become ill from food-related diseases each year resulting in 128,000 hospitalizations, and 3,000 deaths.

According to the CDC, in 2018, the most common forborne illnesses in the United States each year are caused by the following: 

How do you know if you have food poisoning or the stomach flu?

Food poisoning

Food poisoning and the stomach flu may or may not be the same thing, depending if the causative agent is transmitted by contaminated food, or if the agent is transmitted by non-food mechanisms such as body secretions. Most healthcare professionals equate stomach flu to viral gastroenteritis.

Stomach flu

Stomach flu is a non-specific term that describes an illness that usually resolves within 24 hours and is caused commonly by the adenovirus, Norwalk virus, or rotavirus, (rotavirus is most commonly found in children).


If numerous cases of viral gastroenteritis occur in a situation where many people have been eating, it certainly may be considered food poisoning. Norwalk virus is responsible for many cases of foodborne illness outbreaks on cruise ships.

What are the most common infectious types and causes of food poisoning?

The most common causes of food poisoning may be due to infections caused by the following:

  • Bacteria
  • Viruses
  • Parasites
  • Prions (rare)

More than 200 infectious causes exist. Sometimes it is not the bacteria that causes the problem, but rather the toxin that bacteria produce in the food before it is eaten. This is the case with Staphylococcal food poisoning and with botulism.

What causes food poisoning?

There are many causes of food poisoning. Sometimes they are classified by how quickly the symptoms begin after eating potentially contaminated food. Think of this as the incubation time from when food enters the body until symptoms begin. 

How does an E. coli 0157:H7 gut infection spread?

Some "food poisonings" may not be due to toxins or chemicals in food but to infectious agents that happen to contaminate the food. E. coli O157:H7 (hemorrhagic E. coli) usually occurs when contaminated food is eaten, but it also can spread from the following:

  • Contaminated drinking water
  • Contaminated swimming pool
  • Passed from child to child in a daycare center


20 Food Poisoning Dangers: Types, Symptoms, and Treatments See Slideshow

What is the incubation time for large and small intestinal food poisoning?

The large intestine and small intestine have an intermediate incubation from about 1 to 3 days.

Large intestine

Infections of the large intestine or colon can cause bloody, mucousy diarrhea associated with crampy abdominal pain.

  • Campylobacter, according to CDC data, is the number one cause of food-borne disease in the United States.
  • Shigella spp contaminates food and water and causes dysentery (severe diarrhea often containing mucus and blood).
  • Salmonella infections often occur because of poorly or undercooked cooked and/or poor handling of the chicken and eggs. In individuals with weakened immune systems, including the elderly, the infection can enter the bloodstream and cause potentially life-threatening infections.
  • Vibrio parahaemolyticus can contaminate saltwater shellfish and cause watery diarrhea.

Small intestine infection

Diarrhea due to small bowel infections tends not to be bloody, but infections may affect both the small and large intestines at the same time.

  • E. coli (enterotoxigenic) is the most common cause of traveler's diarrhea. It lacks symptoms such as fever or bloody diarrhea.
  • Vibrio cholerae, often from contaminated drinking, water produces a voluminous watery diarrhea resembling rice water.
  • Viruses such as Norwalk, rotavirus and adenovirus tend to have other symptoms associated with an infection including fever, chills, headache, and vomiting.
  • Botulism is caused by Clostridium botulinum toxin and may present with fever, vomiting, mild diarrhea, numbness, and weakness leading to paralysis.

What is the incubation period for E. coli 0157:H7 and Yersinia enterocolitica infections?

Hemorrhagic E. coli 0157:H7 and Yersinia enterocolitica infections have a long incubation period of 3 to 5 days.

  • Hemorrhagic E. coli (mainly E. coli 0157:H7) can cause inflammation of the colon leading to bloody stools. In some children, about a week after infection, it can progress to hemolytic uremic syndrome (HUS). Elderly individuals may contract thrombotic thrombocytopenic purpura (TTP). Toxins from the bacteria enter the bloodstream and hemolyze or destroy red blood cells. In addition, the toxins cause kidney failure and uremia, where waste products build up in the body.
  • Yersinia enterocolitica may cause inflammation of lymph nodes in the lining of the abdomen and may mimic appendicitis.

Some "food poisonings" may not be due to toxins or chemicals in food but to infectious agents that happen to contaminate the food. E. coli O157:H7 (hemorrhagic E. coli) usually occurs when contaminated food is eaten, but it also can spread from:

  • Contaminated drinking water
  • Contaminated swimming pool
  • Passed from child to child in a daycare center

What is the incubation period for chemical and bacterial causes of food poisoning?

Chemical and bacterial infections have a short incubation of less than 16 to 24 hours

Chemical causes

  • Scrombroid poisoning usually is due to poorly cooked or stored fish. The affected person will experience flushing, shortness of breath, and difficulty swallowing within 1 to 2 hours of eating.
  • Ciguatera poisoning is another fish toxin that occurs after eating fish such as grouper, snapper, and barracuda. Symptoms include vomiting and diarrhea, muscle aches, and neurologic complaints including headache, numbness and tingling, hallucinations, and difficulty with balance (ataxia).
  • Mushroom ingestion can cause initial symptoms like vomiting and diarrhea. Eating Amanita mushrooms can cause liver and kidney failure leading to death.

Bacterium Causes

  • Staphylococcus aureus poisoning is due to a toxin that is pre-formed in food before it is eaten. It causes vomiting within 1 to 6 hours after eating the contaminated food.
  • Bacillus cereus is an infection that occurs after eating poorly cooked or raw rice.
  • Clostridium perfringens produces a spore that may germinate in cooked meat that has been stored in an environment that was too warm. Within 8 to 12 hours, it may cause profuse diarrhea.

What is the incubation time for viruses, parasites, bacteria, and other pathogenic infections?


  • Giardiasis may occur after drinking water from lakes or rivers that have been contaminated by beavers, muskrats, or sheep that have been grazing. It also can be passed from person to person, for example in daycare settings.
  • Amoebiasis is encountered in contaminated drinking water, usually in tropical or semitropical climates, and can be passed from person to person.
  • Trichinosis is due to an infection from eating undercooked pork or wild game such as bear meat. Aside from fever and gastrointestinal complaints, symptoms include muscle pain, facial swelling, and bleeding around the eyes and under the fingernails.
  • Cysticercosis is often seen in developing countries where water is contaminated with pork tapeworms and the person swallows the ova from the tapeworm. The infection can invade the brain (neurocysticercosis) causing seizures.
  • Cyclospora is a one-celled parasite that infects the small intestine causing explosive, watery bowel movements. Cyclospora infection is contracted by eating contaminated food or drinking water. Cyclospora infection usually does not spread from person to person. Symptoms may also include headache, body aches, and malaise and can mimic a viral type infection. Without antibiotic treatment, Cyclospora infection will gradually resolve over many weeks but may come and go (relapse) over that period.


  • Listeriosis usually occurs after foods contaminated with Listeria bacteria are ingested. These include unpasteurized, raw milk, soft cheeses, and processed meats and poultry. Vegetables and fruits may also become infected with Listeria. The bacteria may lay dormant in or on the surface of the food products for weeks.
  • Brucellosis occurs by ingesting raw or unpasteurized milk and cheese, especially goat's milk contaminated with Brucella spp


  • Hepatitis A is spread by poor food handling, and not due to blood exposure such as in hepatitis B and C.


  • Toxoplasmosis is usually transmitted to humans from cat feces containing Toxoplasma parasites; most infections are asymptomatic, but people who have diminished immune systems can develop systemic disease symptoms.


  • Bovine Spongiform encephalopathy (mad cow disease) is acquired by eating foods containing prions (transmissible agents that induce abnormal folding of brain protein) contaminating the brain or spinal cord from infected cows.

Who is at a higher risk of getting food poisoning?

Newborns, the elderly, and others with compromised immune systems are at higher risk of becoming ill with Listeria infections. Pregnant women are also at higher risk of contracting Listeria infections, and to avoid infections and prevent giving the infection to the fetus.

Pregnant women are recommended to avoid these foods to reduce the risk of contracting a Listeria infection:

  • Doft cheeses like brie
  • Vamembert
  • Blue (cream cheese is safe)

What are the signs and symptoms food poisoning?

Food poisoning most commonly causes the following:

  • Stomach cramps
  • Vomiting
  • Diarrhea

This can cause significant amounts of fluid loss and diarrhea along with nausea and vomiting may make it difficult to replace lost fluid, leading to dehydration. In developing countries where infectious epidemics cause diarrheal illnesses, thousands of people die because of dehydration.

As noted in the section above, other organ systems may be infected and affected by food poisoning. Symptoms will depend upon what organ system is involved (for example, encephalopathy due to brain infection).

What are the symptoms of food poisoning from undercooked and stored foods?

Other illnesses may involve chemical toxins that are produced in certain foods that are poorly cooked or stored. For example, scombroid and shellfish poisoning are due to a large release of histamine chemicals from the fish when it is eaten. Scombroid poisoning causes symptoms like those of an allergic reaction and may include:

Scombroid poisoning is sometimes confused with a shellfish allergy.

How long does food poisoning last?

Most cases of food poisoning last about 1 to 2 days and symptoms resolve on their own. If symptoms persist longer than that, the person should contact their doctor

Cyclospora infections may be difficult to detect and diarrhea may last for weeks. Doctors may consider this parasite as the potential cause of food poisoning in patients with prolonged symptoms.

When should you call the doctor for food poisoning?

With a clear fluid diet and rest, most infections resolve on their own within 24 hours. A healthcare professional should be contacted if the vomiting and diarrhea are associated with one or more of the following symptoms:

  • Fever
  • Blood in the stools
  • Signs of dehydration include lightheadedness when standing, weakness, and decreased urination
  • Diarrhea that lasts longer than 72 hours
  • Repeated vomiting that prevents drinking and rehydrating (replacing the fluids lost due to fever, diarrhea, and vomiting)

What tests diagnose food poisoning?

Most times, the diagnosis of food poisoning is made by history and physical examination. Often, the patient volunteers the diagnosis when they come for medical care. For example, "I got sick after eating potato salad at a picnic," or, "I drank a raw egg protein shake."

  • Symptoms: The doctor may ask questions about the symptoms, when they started, and how long they have lasted. A review of systems may help give direction as to what type of infection is present. For example, a patient with numbness in their feet and weakness may be asked about whether they have opened any home-canned food recently.
  • Travel history: Travel history may be helpful to see if the patient had been camping near a stream or lake and the potential for drinking contaminated water, or if they have traveled out of the country recently and have eaten different foods than they normally do, such as raw eggs or wild game.
  • Physical examination: Physical examination begins with taking the vital signs of the patient (blood pressure, pulse rate, and temperature). Clinical signs of dehydration include dry, tenting skin, sunken eyes, dry mouth, and lack of sweat in the armpits and groin. In infants, in addition to the above, subtle signs of dehydration may include poor muscle tone, poor suckling, and sunken fontanelle.
  • Blood tests: Routine blood tests are not usually ordered unless there is concern about something more than vomiting and diarrhea. In patients with significant dehydration, the doctor may want to check electrolyte levels in the blood as well as kidney function. If there is concern about hemolytic uremic syndrome, a complete blood count (hemogram, CBC) to check the red blood cells, white blood cells, and platelet count may be ordered. If there is concern about hepatitis, liver function tests may be ordered.
  • Stool samples: Stool samples may be useful especially if there is concern about infections caused by Salmonella, Shigella, and Campylobacter, the common non traveler's diarrhea. This is especially true when the patient presents with bloody diarrhea, thought to be due to infection. If there is concern about a parasite infection, stool samples can be examined also for the presence of parasites. Some parasites may be very difficult to see under the microscope, including Cyclospora, because it is so tiny.
  • Immunological tests: Depending on the suspected cause of the food poisoning, there are some immunological tests (for example, detection of Shiga toxins) that the CDC recommends. Cyclospora DNA may be detected in the stool using molecular testing called polymerase chain reaction (PCR). Other methods may be used (for example, the detection of prions in tissue samples).

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What is the treatment for food poisoning?

The best treatment for food poisoning may include the following:

  • Maintaining good hydration is the priority when treating food poisoning. Hospitalization may be appropriate if the patient is dehydrated or if they have other underlying medical conditions that become unstable because of the fluid or electrolyte imbalance in their body.
  • Medications may be prescribed to help control nausea and vomiting.
  • Medications to decrease the frequency of diarrhea may be indicated, but if food poisoning is suspected, it is best to consult a health-care professional before taking OTC (over-the-counter) medications such as loperamide (Imodium), because it may cause increased problems for the patient.
  • Except for specific infections, antibiotics are not prescribed in the treatment of most food poisoning. Often, the healthcare professional will decide upon their use based on multiple factors such as the intensity of the disease symptoms, the additional health factors of the patient, a serious response to infection (sepsis), and organ system compromise. For example, a pregnant woman suspected of having listeriosis will likely be treated with IV antibiotics because of the effect of the infection on the fetus.
  • Complications of certain types of food poisoning are best treated in consultation with infectious disease specialists (for example, HUS, TTP, and bovine spongiform encephalopathy).

What natural and home remedies treat food poisoning?

The key to home care is being able to keep the person hydrated. Drinking a lot of water or a balanced electrolyte solution such as Gatorade or Pedialyte usually is adequate to replenish the body with fluids. A person can lose a significant amount of fluid with an episode of diarrhea and/or vomiting, and these fluids need to be replaced.

People who show any signs of dehydration such as decreased urination, dizziness, or dry mucous membranes, especially in the young or elderly, should seek medical treatment.

What is the prognosis food poisoning?

Fortunately, most cases of food poisoning are self-limiting and resolve within a few hours to a few days, and the affected individual returns to normal function.

Depending upon the cause of the infection, and the patient's underlying medical condition, the infection may cause significant organ damage and even death.

What are the complications of food poisoning?

The first and most important complication of food poisoning is dehydration. Food poisoning can cause significant loss of body water and changes in the electrolyte levels in the blood.

If the affected individual has underlying medical conditions requiring medication, persistent vomiting may make it difficult to swallow and digest those medications.

Other complications of food poisoning are specific to the type of infection. Some are listed in the causes of food poisoning such as HUS, TTP, or encephalopathy.

Can you die from food poisoning?

Listeria is a type of bacteria that has caused the two most deadly outbreaks of food poisoning in United States history. In 1985, an outbreak in California was traced to eating a type of fresh cheese, and in 2011, Listeria food poisoning was traced to a cantaloupe farm and processing operation in Colorado.

Listeria most often is associated with the following:

  • Soft cheeses
  • Raw milk
  • Contaminated fruits, vegetables, poultry, and meats

Tips to prevent food poisoning

7 food safety tips

Prevention of foodborne illness begins at home with proper food preparation techniques.

  1. Foods should be cooked thoroughly. This especially applies to raw meat, eggs, and poultry. A meat thermometer can be used to measure the internal temperature of a meat dish.
  2. Leftovers should be refrigerated immediately so bacteria and viruses do not have time to start growing.
  3. Wash fruits and vegetables well before eating. This removes dirt, pesticides, chemicals, or other infectious agents used on, or exposed to, the foods in the fields or storage facilities.
  4. Wash hands routinely before and after handling food to help prevent the spread of infection.
  5. Thoroughly clean counters and other areas that are used to clean, prepare, and assemble foods. Cross-contamination of food is common and can cause food poisoning. For example, a cutting board and knife used to cut raw chicken should be washed thoroughly before cutting up fruit and vegetables to prevent the spread of Salmonella.
  6. In restaurants, meals are prepared by others. Health inspectors check restaurants routinely and their reports on sanitary practices are usually available online. Make certain the food ordered is thoroughly cooked, especially meats such as hamburgers.
  7. Pregnant women and people who have compromised immune systems, such as those undergoing chemotherapy or who are taking medication such as prednisone, should avoid eating soft cheeses like camembert, brie, blue, and feta because of the risk of contracting Listeria. Be very sure all fruits and vegetables are cleaned thoroughly before eating, no matter the source.
Medically Reviewed on 7/12/2023
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United States. Centers for Disease Control and Prevention. "Estimates of Foodborne Illness in the United States." Nov. 5, 2018. <>.

U.S. Food & Drug Administration. "Foodborne Illnesses: What You Need to Know." Sept. 5, 2018. <>.