What Causes Food Poisoning?

Foods and Associated Pathogens

Medically reviewed by Josephine Hessert, DO

Food poisoning, also called foodborne illness, is irritation or infection of the digestive tract. It is commonly caused by bacteria, viruses, and parasites in food and beverages.

Symptoms of food poisoning commonly include nausea, vomiting, abdominal pain, and/or diarrhea that can be managed at home. However, more severe symptoms like blurred vision, paralysis, and dehydration require immediate medical treatment.

This article looks at common causes of food poisoning and how to avoid it.

<p>GMVozd / Getty Images</p>

GMVozd / Getty Images

What Causes Food Poisoning: A List of Foods and Cook Temps

Certain foods, like meat and dairy, are more likely to cause food poisoning, especially if they aren't prepared properly.

Poultry and Meat

Poultry, which includes chicken and turkey, is often contaminated with germs like Salmonella, Campylobacter, and Clostridium perfringens. Meat, including beef, pork, lamb, and goat, commonly contains Salmonella and Escherichia coli (E. coli).

These germs can be eliminated by cooking poultry and meat properly, which includes:

  • Poultry: Cook to an internal temperature of at least 165 degrees F (all temperatures mentioned are in Fahrenheit).

  • Whole meats (roasts, chops, and steak): Cook to a minimum internal temperature of 145 degrees, measured with a food thermometer in the thickest part. The meat should rest for three minutes before carving or eating.

  • Ground meat (hamburgers and sausage) must reach 160 degrees before consuming.

Raw meat and poultry should be kept away from fresh produce and precooked foods. Refrigerate leftovers at 40 degrees or colder within two hours of preparation. If the food is exposed to a temperature of 90 degrees or higher, refrigerate leftovers within one hour.

Related: Salmonella: Food Safety Practices and Proper Cooking Temperatures


Fresh eggs, even with clean, uncracked shells, may contain Salmonella.

Raw eggs should be cooked until the yolk and white are firm. Egg dishes, such as quiche, should reach a minimum internal temperature of 160 degrees. Casseroles that contain eggs and meat should be cooked to at least 165 degrees.

Other tips to avoid foodborne illness from eggs include:

  • Store eggs in the refrigerator at a minimum of 40 degrees.

  • Do not taste or eat raw batter or cookie dough prepared with raw eggs.

  • Eat hard-boiled eggs within one week of cooking.

  • When preparing dishes that include raw or undercooked eggs when served, like homemade ice cream, choose eggs that have been treated to destroy Salmonella through pasteurization.

  • Refrigerate cooked eggs or egg dishes within two hours.

Fruits and Vegetables

Some raw fruits and vegetables contain harmful bacteria, including SalmonellaE. coli, and Listeria.

The safest way to prepare fruits and vegetables is to fully cook them. If eating raw or not thoroughly cooked produce, wash it well. In fact, all produce should be washed, even if you do not plan to eat the peel.

When shopping for and preparing produce, keep the following tips in mind:

  • Choose fruits and vegetables that aren't bruised or damaged.

  • When buying precut produce, choose products that have been kept cold.

  • Separate produce from raw meat in your shopping cart, grocery bags, and refrigerator.

  • Wash fruits and vegetables well under running water before eating them.

  • Cut or remove any bruised or damaged areas before preparing.

  • Refrigerate fruits and vegetables within 2 hours after cooking, peeling, or cutting.

Eating undercooked or raw sprouts may cause food poisoning. The warm, humid conditions in which sprouts are grown can be a breeding ground for germs to grow and multiply. Cook alfalfa, bean, and clover sprouts until they are steaming hot to lower the risk of contamination.

Unpasteurized Dairy

Raw or unpasteurized milk and dairy products can carry many harmful germs, including SalmonellaCampylobacterCryptosporidiumE. coliListeria, and Brucella.

Unlike raw milk, pasteurized milk goes through a process that heats the raw milk to a temperature high enough to kill harmful bacteria. Purchase pasteurized dairy products, and avoid eating ice cream, yogurt, pudding, and soft cheeses such as Brie and queso blanco made from unpasteurized milk.


Raw or undercooked seafood, including fish with fins and shellfish like oysters, can be contaminated with norovirus and Vibrio.

To reduce the risk of foodborne illness from seafood, cook salmon, tuna, trout, and other fish to a minimum internal temperature of 145 degrees or until the flesh is no longer translucent and flakes easily.

Cook shrimp, crab, lobster, and scallops until the flesh is entirely opaque. Clams, oysters, and mussels should be boiled until their shells open (about three minutes). All leftover seafood should be heated to a minimal internal temperature of 165 degrees.

Avoid raw or undercooked seafood, including sashimi, some sushi, and ceviche. Always keep raw seafood away from ready-to-eat food and refrigerate within two hours after preparation.

Raw Flour

Although flour doesn't necessarily look like raw food, most flour is raw. This means it hasn't been treated to kill germs such as E. coli and Salmonella that cause food poisoning.

Always cook foods made with flour thoroughly and avoid tasting or eating raw dough or batter. Wash your hands and countertops after handling flour and raw dough.

Related: What to Eat After Food Poisoning to Heal Your Gut

Strains of Bacteria That Cause Food Poisoning

Several germs, bacterial strains, and viruses can cause food poisoning.


Campylobacter food poisoning is commonly caused by consuming raw milk, chicken, shellfish, turkey, or contaminated water. Symptoms, including diarrhea, vomiting, cramps, and fever, typically develop within two to five days of exposure and last around one week.

Clostridium Perfringens

The bacterium Clostridium perfringens is among the most common causes of food poisoning. C. perfringens is commonly found in beef, poultry, gravies, and foods kept at unsafe temperatures.

Symptoms include diarrhea and stomach cramps without vomiting or fever. They can develop within six hours to a day of consuming the contaminated food and last for around 24 hours. However, in some cases, symptoms may last for up to two weeks.

Escherichia Coli

People can develop an E. coli infection after consuming undercooked meat, raw milk or produce, or contaminated water. This foodborne illness can also spread through improper handwashing.

Infection with E. coli usually causes severe bloody diarrhea, stomach pain, and vomiting within three to four days of exposure. Symptoms last anywhere from five to 10 days.

Rarely, symptoms may progress to hemolytic uremic syndrome (HUS). It's most common in children under age 10 and can cause kidney failure, damage to the lining of blood vessel walls, and a breakdown of red blood cells.


Listeria is a type of bacteria commonly found in unpasteurized dairy products and raw fruits and vegetables like sprouts. Other sources include ready-to-eat deli meat, hot dogs, and refrigerated meat spread or smoked seafood.

Listeria can cause diarrhea and fever, similar to other foodborne illnesses. However, when listeria spreads beyond the intestines, known as invasive listeriosis, it can cause severe symptoms, including:

Symptoms generally begin within a few weeks and can last for days to weeks. Infection during pregnancy can lead to miscarriage, stillbirth, or premature delivery.


You can get infected with norovirus by accidentally ingesting foods or beverages contaminated with tiny particles of stool or vomit from an infected person. It can also spread through direct contact or touching contaminated surfaces and putting your unwashed hands in your mouth.

This highly contagious virus causes symptoms like diarrhea, vomiting, and stomach pain within 12 to 48 hours after exposure. Symptoms typically last one to three days but may last longer in children, older adults, and hospitalized patients.


Several foods, including meat, poultry, eggs, raw produce, and nuts, have been linked to salmonella. Food poisoning from salmonella causes diarrhea, stomach cramps, fever, and vomiting six hours to six days after exposure. Symptoms typically last for four to seven days.

What Causes Severe Food Poisoning in Some People?

While anyone can get food poisoning, some people are more likely to become infected and get very sick. Certain factors make it more difficult for your body to fight germs and viruses effectively.

Groups at a higher risk of severe food poisoning include:


Food poisoning can be especially dangerous for children because it can cause vomiting and diarrhea, and children can quickly become dehydrated. The following signs of dehydration in small children include:

  • Dry mouth and thirst

  • Decreased energy

  • Urinating less frequently, no wet diapers in three hours or more

  • No tears are produced when crying

  • Sunken eyes or cheeks

  • Decreased skin turgor

How to Avoid the Causes of Food Poisoning

Here are some measures you can take to help reduce your risk of food poisoning:

  • Wash your hands and all cooking surfaces before, during, and after cooking.

  • Separate raw meat, poultry, eggs, and seafood from ready-to-eat foods by using different cutting boards and storing different types of food away from one another in the refrigerator.

  • Always cook foods to a safe minimum internal temperature.

  • Check the temperature of foods by inserting a food thermometer into the thickest part, avoiding bones and fat.

  • Keep your refrigerator at or below 40 degrees.


Food poisoning is an illness caused by eating foods contaminated with pathogens, or germs. It commonly causes cramps, diarrhea, nausea, and vomiting. In rare cases, however, it may lead to neurological symptoms that require immediate medical treatment.

Poultry, meat, raw dairy products, seafood, eggs, and raw produce are the most common culprits of foodborne illness, especially when not stored and/or cooked properly. To reduce your risk of foodborne illness, practice safe food handling, cooking, and storage.

Read the original article on Verywell Health.