Food Poisoning

What is food poisoning?

Food poisoning (foodborne illness) is caused by bacteria, parasites, or viruses found in food.

Millions of Americans get food poisoning each year.

Food poisoning symptoms often look like stomach flu (gastroenteritis). Many people with a mild case think they have stomach flu or a virus.

What causes food poisoning?

Most food poisoning is caused by eating food that has certain types of bacteria, parasites, or viruses. When you eat these foods, the bacteria keep growing in your digestive tract. This causes an infection.

Foods can also make you ill if they have a toxin or poison made by bacteria growing in the food.

Several types of bacteria can cause food poisoning. Among the more common bacteria are:

Salmonella and Campylobacter

  • May be found in meat, poultry, and eggs that are raw or not cooked long enough (undercooked)

  • Can be found in dairy products that haven’t gone through a high-heat process to kill bacteria (are unpasteurized)

  • Can be found in raw fruits and vegetables

Clostridium perfringens

  • May be found in raw meat, poultry, eggs, or unpasteurized dairy foods

  • Can be found in vegetables and crops that have touched soil

  • Can cause food poisoning when soups, stew, and gravies made with meat, fish, or poultry are left at room temperature and not refrigerated for long periods of time.


  • May be found in unpasteurized milk and soft cheeses made with unpasteurized milk

  • May also be found in deli meats, hot dogs, and store-made deli salads

  • Can be found in raw sprouts and melons

Staphylococcus aureus

  • Can spread to food when touched by someone with the bacteria who has not washed their hands before handling the food.

  • Can cause infection when foods not cooked after handling, such as sliced meats, puddings, pastries, and sandwiches are risky if contaminated.

Escherichia coli (E. coli)

  • Can cause infection if you eat beef that is undercooked, mainly ground beef

  • Can be found in unpasteurized milk

  • Contaminated raw fruits and vegetables

  • Can be found in food or water that is contaminated

You can also get food poisoning from viral diseases, such as hepatitis A. These viral diseases:

  • Can pass from an infected person’s hands to the hands of food workers or into wastewater (sewage)

  • Can spread when raw or undercooked shellfish and raw produce, and other uncooked foods that have touched unsafe, dirty water

Clostridium botulinum

Botulism is a rare but deadly form of food poisoning. It is caused by the bacteria (clostridium botulinum) that is found all over, even in soil and water. 

Botulism can happen when:

  • You eat low-acid foods that are not correctly canned or preserved at home. These foods include meat, fish, poultry, or vegetables.

  • Infants eat raw honey or corn syrup. Babies younger than 1 year old should never have honey or corn syrup.


Norovirus is a common virus that is often mistaken for the "stomach flu." It is very contagious.

Norovirus food poisoning can happen when:

  • You have direct contact with someone else with norovirus. This includes caring for someone with norovirus, eating food handled by them, or sharing food or eating utensils with them.

  • Eating food or drinking beverages contaminated with norovirus.

  • Touching objects or surfaces contaminated with norovirus and then putting your fingers in your mouth before washing them.

Who is at risk for food poisoning?

Anyone can get food poisoning. But some people are more likely to get it than others. They are also at greater risk of getting very ill from it. This is because their body’s disease-fighting system (immune system) doesn’t work well.

People who are at greater risk include:

  • Young children (younger than 5 years).  Their immune systems aren’t fully developed yet.

  • Older adults (age 65 and older). As people age their body's immune system response grows weaker. Age-related changes in our senses of taste and smell also make it easier to eat contaminated food by mistake. 

  • Pregnant women. A woman’s immune system changes during pregnancy. The unborn baby is also at risk.

  • People with long-term (chronic) disease.  People with diseases, such as diabetes or cancer, have a weaker immune system. People with HIV/AIDS, organ transplants, liver disease, or certain autoimmune diseases may also be at risk. Certain medicines used to treat these chronic diseases also suppress the immune system.

What are the symptoms of food poisoning?

Food poisoning symptoms can look like the symptoms of stomach flu (gastroenteritis). Many people with mild cases of food poisoning think they have stomach flu.

The time it takes food poisoning symptoms to start can vary. Illness often starts in about 1 to 3 days. But symptoms can start any time from 30 minutes to 3 weeks after eating contaminated food. The length of time depends on the type of bacteria or virus causing the illness.

Each person’s symptoms may vary. Symptoms can range from very mild to very serious. They can last from a few hours to several days. Symptoms may include:

  • Belly cramps

  • Watery or bloody diarrhea

  • Nausea and vomiting

  • Headache

  • Fever

  • Belly bloating and gas

Food poisoning symptoms may look like other health problems. Always see your healthcare provider to be sure.

How is food poisoning diagnosed?

Your healthcare provider will ask you when you became sick, what your symptoms are, and what foods you have eaten.

Your provider will also look at your past health. They will give you a physical exam.

You may have lab tests to find out what bacteria caused your illness. In some cases, the cause can’t be found. Unless many people sit down to the same meal and all become ill, your provider will have a hard time diagnosing the foodborne illness.

How is food poisoning treated?

Most mild cases of food poisoning are treated the same as stomach flu (gastroenteritis) and usually last less than a week. If you have diarrhea or vomiting, you may lose a lot of fluids (get dehydrated). The goal is to replace your lost fluids and ease your symptoms. You may also be prescribed anti-nausea medicine to prevent vomiting.

For some types of bacterial food poisoning, your healthcare provider may give you a medicine that fights bacteria (an antibiotic). Antibiotics don’t work on infections caused by a virus.

In severe cases, you may need to be hospitalized.

Call your healthcare provider or get medical care if you can’t keep fluids down or if your symptoms don’t go away.  

What can I do to prevent food poisoning?

To prevent food poisoning, wash your hands often. Also prepare and store food safely.

Always wash your hands after:

  • Using the toilet

  • Changing diapers

  • Smoking

  • Blowing your nose

  • Coughing or sneezing

  • Touching animals

When preparing food, be sure to:

  • Wash your hands for at least 20 seconds with soap and clean, running water before and after touching raw meat, poultry, shellfish, fish, eggs, or produce

  • Wash all fruits and vegetables well before eating

  • Use plastic cutting boards for cutting raw fish, poultry, or meat. They are easier to keep clean.

  • Wash all utensils and surfaces with soapy water before and after they are used to prepare food. One quart of water mixed with 1 teaspoon of bleach can be used to sanitize surfaces and utensils.

  • Cook poultry, beef, and eggs to the correct temperature before eating

  • Keep raw meat, poultry, seafood, and their juices away from other foods

  • Use a meat thermometer to make sure that foods are cooked to an appropriate internal temperature

When choosing food:

  • Do not have any food made from unpasteurized milk or juice.

  • Do Not have any food made from raw or undercooked eggs, poultry, and meat.

When storing food, be sure to:

  • Refrigerate or freeze raw and cooked perishable foods right away. If they are at room temperature for more than 2 hours, consider them unsafe to eat.

  • Set refrigerators at 40°F (4°C) or below and freezers at 0°F (-17°C).

  • Keep fruits and vegetables, cooked foods, and prepared foods away from raw meat and raw eggs.

  • Refrigerate mayonnaise, salad dressings, and any foods that have them.

  • Throw out food if you don’t know how long it’s been left out of the fridge.

  • Throw out food if you’re not sure it is bad.

Key points about food poisoning

  • Food poisoning is caused by bacteria, parasites, and viruses found in food.

  • Symptoms may look like stomach flu (gastroenteritis).

  • Treatment focuses on replacing fluids and easing nausea and vomiting.

  • In severe cases, you may need to be hospitalized.

  • To prevent food poisoning, wash your hands often. Also prepare and store food safely.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

  • Know the reason for your visit and what you want to happen.

  • Before your visit, write down questions you want answered.

  • Bring someone with you to help you ask questions and remember what your provider tells you.

  • At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

  • Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are.

  • Ask if your condition can be treated in other ways.

  • Know why a test or procedure is recommended and what the results could mean.

  • Know what to expect if you do not take the medicine or have the test or procedure.

  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.

  • Know how you can contact your healthcare provider if you have questions.

Online Medical Reviewer: Brittany Poulson MDA RDN CD CDE
Online Medical Reviewer: Heather M Trevino BSN RNC
Online Medical Reviewer: Rita Sather RN
Date Last Reviewed: 2/1/2024
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