Symptoms & Causes of Food Poisoning

On this page:

• What are the symptoms of food poisoning?
• What are the symptoms of dehydration?
• Seek care right away
• What causes food poisoning?
• What kinds of microbes cause food poisoning?
• How do harmful chemicals cause food poisoning?

What are the symptoms of food poisoning?

Common symptoms of food poisoning include

• diarrhea or bloody diarrhea
• vomiting
• pain in your abdomen
• fever
• headache

Symptoms range from mild to severe and may last from a few hours to several days.

Less commonly, some types of food poisoning—such as botulism and fish and shellfish poisoning—can affect your nervous system. Symptoms may include

• blurred vision
• headache
• paralysis
• tingling or numbness of your skin
• weakness

People with nervous system symptoms should see a doctor or go to an emergency room right away.

What are the symptoms of dehydration?

Symptoms of dehydration, the most common complication of food poisoning, may include the following in adults

• extreme thirst and dry mouth
• urinating less than usual
• light-headedness; dizziness, which may occur when the person stands up; or fainting
• feeling tired
• dark-colored urine
• decreased skin turgor, meaning that when you pinch and release the person’s skin, it does not flatten back to normal right away
• sunken eyes or cheeks

If you are the parent or caretaker of an infant or a young child with symptoms of food poisoning, you should watch for the following signs of dehydration

• thirst and dry mouth
• urinating less than usual, or no wet diapers for 3 hours or more
• lack of energy
• no tears when crying
• decreased skin turgor, meaning that when you pinch and release the child’s skin, it does not flatten back to normal right away
• sunken eyes or cheeks

Anyone with signs or symptoms of dehydration should see a doctor or go to an emergency room right away. A person with severe dehydration may need treatment at a hospital.

Seek care right away

Food poisoning can become dangerous if it leads to severe dehydration or other complications. The symptoms listed below may suggest that an adult or child has a severe form of food poisoning, dehydration or other complications, or a serious health problem other than food poisoning. Anyone with these signs or symptoms should see a doctor right away.

Adults

Adults with any of the following symptoms should see a doctor right away

• change in mental state, such as irritability, lack of energy, or confusion
• high fever
• vomiting often
• six or more loose stools in a single day
• diarrhea that continues for more than 3 days
• nervous system symptoms
• severe pain in the abdomen or rectum
• stools that are black and tarry or contain blood or pus
• symptoms of dehydration or other complications

Adults should also see a doctor if they aren’t able to drink enough liquids or oral rehydration solutions—such as Pedialyte, Naturalyte, Infalyte, and CeraLyte—to prevent dehydration or if they do not improve after drinking oral rehydration solutions.

Older adults, pregnant women, and adults with a weakened immune system or another health condition should also see a doctor right away if they have any symptoms of food poisoning.

Infants and children

If an infant or child has signs or symptoms of food poisoning, don’t hesitate to call a doctor for advice. Diarrhea is especially dangerous in newborns and infants, leading to severe dehydration in just a day or two. A child with symptoms of dehydration can die within a day if left untreated.

If you are the parent or caretaker of an infant or child with any of the following signs or symptoms, seek a doctor’s help right away

• change in the child’s mental state, such as irritability or lack of energy
• diarrhea lasting more than a day
• any fever in infants
• high fever in older children
• frequent loose stools
• vomiting often
• nervous system symptoms
• severe pain in the abdomen or rectum
• signs or symptoms of complications, such as dehydration or hemolytic uremic syndrome
• stools that are black and tarry or contain blood or pus

You should also seek a doctor’s help right away if a child has signs or symptoms of food poisoning and the child is an infant, was born prematurely, or has a history of other medical conditions. Also seek a doctor’s help right away if the child is not able to drink enough liquids or oral rehydration solutions to prevent dehydration or if the child does not improve after drinking oral rehydration solutions.

What causes food poisoning?

Infections with microbes—viruses, bacteria, and parasites—cause most food poisoning.² Harmful chemicals also cause some cases of food poisoning.

Microbes can spread to food at any time while the food is grown, harvested or slaughtered, processed, stored, shipped, or prepared.

Some harmful microbes may already be present in foods when you buy them. Foods that may contain microbes include

• fresh produce
• raw or undercooked meat, poultry, and eggs
• dairy products and fruit juices that have not been pasteurized—heated to kill harmful microbes
• fish and shellfish
• foods that people handle during preparation, sometimes called “deli foods,” such as sliced meat, salads and cut fruit, sandwiches, and baked goods
• processed and ready-to-eat meats such as hot dogs or deli meat
• foods that are not properly canned or sealed

If you don’t keep raw foods—such as beef, poultry, seafood, and eggs—separate from other foods, microbes from the raw foods can spread to other foods. Microbes can also spread from raw foods to your hands, kitchen utensils, cutting boards, and kitchen surfaces during food preparation. If you don’t wash your hands, utensils, cutting boards, and surfaces completely after they have come into contact with raw foods, they can spread microbes to other foods.

Microbes can cause food poisoning if you don’t take steps to kill or slow the growth of microbes in food. Microbes can grow if people don’t cook food thoroughly, keep cooked food hot, or promptly refrigerate or freeze food that can spoil.

Microbes present in the stool or vomit of people who are infected can also spread to food and cause food poisoning. People may spread these microbes to foods and drinks, especially if they don’t wash their hands thoroughly after using the bathroom, after changing a diaper, and before preparing foods and drinks.

Find tips to keep food safe and help prevent food poisoning.

What kinds of microbes cause food poisoning?

Viruses

Viruses invade normal cells in your body. Many viruses cause infections that can be spread from person to person.

If water comes into contact with stools of infected people, the water may become contaminated with a virus. The contaminated water can spread the virus to foods. For example, if contaminated water is used to water or wash produce, the virus can spread to the produce. Similarly, shellfish that were living in contaminated water could contain a virus.

If people who are infected with a virus prepare or handle foods, they may spread the virus to the foods.

Common viruses that cause food poisoning include norovirus and hepatitis A.

Bacteria

Bacteria are tiny organisms that can cause infection or disease. Bacteria can enter your body through contaminated food or water.

Bacteria grow quickly when the temperature of food is between 40 and 140 degrees. Keeping food colder than 40 degrees in a refrigerator or freezer can slow or stop the growth of bacteria. Cooking food thoroughly often kills bacteria.

Many types of bacteria can cause food poisoning, including

• certain types of Salmonella
• certain types of Clostridium, including the common C. perfringens and the less common C. botulinum, which causes an illness called botulism
• certain types of Campylobacter, including C. jejuni
• Staphylococcus aureus, also called staph
• Escherichia coli, also called E. coli
• certain types of Vibrio
• Listeria monocytogenes, also called Listeria

Parasites

Parasites are tiny organisms that live inside other organisms. Parasites can enter your body through food or water and settle in your digestive tract. In developed countries such as the United States, parasitic infections are rare.

Parasites that cause food poisoning include

• Toxoplasma gondii, which causes an illness called toxoplasmosis
• Giardia
• Cryptosporidium, which causes an illness called cryptosporidiosis or crypto

Travelers’ diarrhea

People who travel from the United States to developing countries may develop travelers’ diarrhea. Eating food or drinking water contaminated with bacteria, parasites, or viruses causes travelers’ diarrhea. Although travelers’ diarrhea is most often acute, some parasites cause diarrhea that lasts longer.

How do harmful chemicals cause food poisoning?

Harmful chemicals may be present in certain foods, including

• fish and shellfish that contain toxins produced by algae or bacteria
• certain types of wild mushrooms
• unwashed produce that contains large amounts of chemical pesticides