Food poisoning is a foodborne illness in which a person gets sick from something they have eaten or drank. Resting and drinking plenty of fluids can help people recover from food poisoning.

Food poisoning refers to gastroenteritis, a condition involving inflammation of the lining of the gut caused by pathogens, or germs, in food or drink.

The Food and Drug Administration (FDA) cites that even though the U.S. food supply has high standards, about 48 million cases of foodborne illnesses occur annually due to eating food containing an infectious pathogen. There are also 128,000 hospitalizations and 3,000 deaths as a result of food poisoning.

This article discusses the common symptoms, causes, and treatment of food poisoning.

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Gastroenteritis is a condition involving inflammation of the lining of the gut — in particular, of the stomach and intestines.

It usually results from pathogens that infect a person and cause symptoms. These are usually viruses, bacteria, or parasites. When the source of such infection is food, it is called food poisoning.

People may also refer to gastroenteritis as “gastric flu” or “stomach flu.” The most common symptoms are usually:

It can also lead to dehydration, especially in people who are very young or older individuals.

The onset of gastroenteritis symptoms after eating food affected by a pathogen can be within a few hours. However, the incubation period can also be much longer, depending on the pathogen involved.

Four well-known, classic symptoms are typical:

These symptoms can occur in any combination. They generally have a sudden (acute) onset, but this can vary along with symptom severity.

Vomiting typically occurs earlier on. Diarrhea usually lasts for a few days but can be longer depending on the organism causing the symptoms.

In addition to the classic symptoms above, gastroenteritis can also lead to:

  • loss of appetite
  • fever or high temperature and chills

Symptoms by type

The type of gastrointestinal symptoms is a clue to the type of infection. Viral infection generally produces diarrhea without blood or mucus, and watery diarrhea is a prominent symptom.

Conversely, a person is more likely to have diarrhea with mucus and blood in bacterial diarrhea. Norovirus can cause acute onset of vomiting, especially in children.

Dehydration and malnutrition

One of the complications of food poisoning and gastroenteritis — especially in very young, older, or otherwise vulnerable people — is the loss of fluids resulting from diarrhea and vomiting, which can lead to dehydration. However, it is possible to prevent dehydration.

In the case of parasitic gastroenteritis, another potential complication is malnutrition. The parasites reach the intestines and feed off the nutrients people absorb from their food. This results in a person developing a chronic lack of nutrients.

Infections can pass from person to person when someone transmits a pathogen by touching food, especially in cases where hand hygiene is more challenging. There are generally viruses, bacteria, or parasites.

Viral gastroenteritis

Viral gastroenteritis is also called stomach flu.

Viruses that most commonly cause viral gastroenteritis are:

  • rotavirus, which is more common in children and the most common cause of viral gastroenteritis in children
  • norovirus, which is more common in adults

Less common viral causes are astroviruses, which usually affect children and older people, and adenoviruses. Cytomegalovirus can cause gastroenteritis, especially in people with weakened immunity.

Bacterial gastroenteritis

The microorganisms that most commonly cause bacterial gastroenteritis are:

A study from the Centers for Disease Control and Prevention (CDC)’s Interagency Food Safety Analytics Collaboration found that, between 2015 and 2019, 75% of E. coli cases came from beef and leafy green vegetables.

Parasitic gastroenteritis

Parasites are organisms that need to live inside and feed off other organisms to survive.

Though gastroenteritis caused by parasites is more common in low and middle-income regions, parasitic infections do occur globally. About 450 million people around the world become ill annually.

The two types of parasites that typically infect the human gastrointestinal tract are single-celled protozoa and helminths, which are worm parasites. Common protozoa infections include giardiasis and cryptosporidiosis.

Learn about parasitic infections in humans.

The time it takes for symptoms to appear may depend on the bacteria or pathogen causing the illness.

Though different pathogens will affect the body in different ways, the FDA and CDC summarize how common pathogens might cause gastroenteritis as follows:

PathogenTime before symptoms startTime symptoms lastCommon food sources
Bacillus cereus10 to 16 hours24 to 48 hoursmeat, stew, gravy, vanilla sauce
Campylobacter jejuni2 to 5 days2 to 10 daysuncooked poultry, unpasteurized milk, water containing pathogens
E. coli1 to 3 days3 to 7 daysuncooked meat (usually beef), raw leafy green vegetables such as lettuce, unpasteurized milk, water containing pathogens
Rotavirus 2 days3 to 8 daysany food containing pathogens from fecal matter
Norovirus12 to 48 hours1 to 3 daysraw oysters, fruit, and vegetables washed in dirty water
Cryptosporidium2 to 10 days1 to 2 weeksany food or water containing pathogens
Giardia1 to 2 weeks1 to 3 weeksany food or water containing pathogens

Gastroenteritis and food poisoning usually resolve without any medical intervention. Treatment focuses on reducing the symptoms and preventing complications, especially dehydration.

The main treatment and prevention strategy for food poisoning is to rest and replace lost fluids and electrolytes by:

  • drinking plenty of liquids, preferably with rehydration salts to replace lost electrolytes — see below
  • ensuring fluid intake even if vomiting persists by sipping small amounts of water or allowing ice cubes to melt in the mouth
  • gradually starting to eat again

What should a person eat?

There are no specific restrictions on food, but bland foods might be easier to digest. These can include:

A person may want to avoid fatty, sugary, or spicy foods, as well as dairy products, caffeine, and alcohol, as these may worsen symptoms.

How to prevent dehydration?

To help avoid the dangerous and potentially fatal effects of dehydration from diarrhea, a person can drink oral rehydration salts (ORS).

Research shows that using ORS prevented more than 50 million deaths from diarrhea worldwide between 2007 and 2018.

Dehydration has been a more significant risk in low- or middle-income countries. In higher-income countries, while the risk of death is smaller, rehydration is nonetheless important.

A person can replace salt, glucose, and minerals lost through dehydration through sachets of oral rehydration salts available from pharmacies and online. They can dissolve the salts in drinking water and do not require a doctor’s prescription.

It is important to get the right concentration, as too much sugar can worsen diarrhea, while too much salt can be extremely harmful, especially for children.

A more diluted solution — for instance, using more than 1 liter of water — is preferable to a more concentrated solution.

Store-bought products such as Pedialyte and Gatorade also help restore electrolytes and increase hydration.

Drug treatments for gastroenteritis

Drugs are available to help reduce the main symptoms of gastroenteritis, which are diarrhea and vomiting:

Antidiarrheals are available over the counter, while antiemetics are available via a prescription.

It is advisable for a person to speak with a doctor before taking antidiarrhea medication, as some infections may worsen with these drugs.

If a person’s stomach flu is due to bacteria, they may also need to take antibiotics.

Probiotics and gastroenteritis

Probiotics (live “good” bacteria and yeasts) may also be helpful in treating gastroenteritis, according to some newer research.

A 2022 study found that the use of probiotics in children hospitalized for acute gastroenteritis shortened the duration of diarrhea by a mean of 1.16 days.

The study used the following strains of beneficial bacteria in the treatment of gastroenteritis in children:

  • Streptococcus thermophilus
  • Lactobacillus rhamnosus
  • Lactobacillus acidophilus
  • Bifidobacterium lactis
  • Bifidobacterium infantis

This is a new area of study, so there may be more future research about using probiotics to help treat gastroenteritis.

People with a weakened immune system are especially at risk of getting food poisoning and experiencing severe symptoms, as their bodies may not be able to fight off the infection as effectively.

Other people at risk include those over the age of 65, pregnant people, children, and infants.

In addition, a person who eats the following foods may be more at risk:

  • beef, chicken
  • fish — especially raw, such as sushi — and seafood, such as shellfish
  • fruit and vegetables
  • sprouts
  • raw flour
  • eggs

Standard advice to avoid food poisoning includes four key components:

  • Cook: Ensure adequate heating time at the proper temperature to kill any bacteria that could cause gastroenteritis. It is helpful to use a thermometer to test cooked meat and to ensure egg yolks are firm.
  • Separate: Separate foods to avoid cross-contamination, especially raw meat.
  • Chill: Chilled storage slows the growth of harmful bacteria.
  • Clean: Keep utensils and worktops clean and wash hands frequently, especially before eating or touching the mouth and after handling raw meat or eggs.

Food poisoning is usually easy to diagnose based on the symptoms alone, with little need for confirmation from a doctor. The symptoms a person reports are usually sufficient to inform a diagnosis.

In some cases, stool testing is necessary. For example, if someone experiences diarrhea along with blood or it is watery for more than a few days, doctors may want a stool sample to test for parasites or bacteria.

During an outbreak of rotavirus, for example, the doctor may request other specific tests.

Sometimes, based on a person’s symptoms or history, a doctor may rule out other conditions, such as:

The following are answers to common questions about food poisoning.

What are other causes of gastroenteritis?

Food poisoning is the most common cause of gastroenteritis. In rarer cases, a few other causes can lead to gastroenteritis. These include eating food containing heavy metals and eosinophilic gastroenteritis, which is a sensitivity or allergy to certain foods.

Sometimes, when a person eats food containing bacteria, they may not get sick from the bacteria itself but from a toxin the bacteria releases.

Is it food poisoning or stomach flu?

Food poisoning refers to gastroenteritis caused by eating food containing pathogens.

This can have a viral cause, such as norovirus for example, which is when it is known as stomach flu. However, this is not what people think of as the “flu,” which is the influenza virus.

Learn more about stomach flu vs influenza.

Is food poisoning contagious?

Yes, food poisoning can pass from person to person. Food poisoning refers to gastroenteritis that results from ingesting pathogens (germs) in food, and gastroenteritis is transmissible between people.

How transmissible gastroenteritis is can depend on the type of pathogen and the amount a person has been exposed to. It may also depend on any predisposing factors, such as whether the person is immunocompromised.

A person who is ill to others while they have symptoms and for several weeks after getting better.

People can contract the infection by touching water, food, or other objects infected with pathogens. A person can also pass it on by coming into physical contact with another individual or by breathing out droplets containing the pathogen.

Learn more about contracting stomach flu.

Food poisoning is a foodborne sickness due to ingesting pathogens in food or drink. It usually refers to gastroenteritis, or stomach inflammation, that results from these pathogens.

Treatment for food poisoning involves getting plenty of rest and drinking lots of fluids. Using oral rehydration salts can help prevent dehydration if a person is experiencing vomiting and diarrhea.

Food poisoning will usually resolve on its own in a few days. It is best to contact a doctor about food poisoning if a person has weakened immunity or symptoms last longer than 1 week.