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What is food poisoning?
Food poisoning is an illness caused by eating foods that have harmful organisms in them. These harmful germs can include bacteria, parasites, and viruses. They are mostly found in raw meat, chicken, fish, and eggs, but they can spread to any type of food. They can also grow on food that is left out on counters or outdoors or is stored too long before you eat it. Sometimes food poisoning happens when people don't wash their hands before they touch food.
Most of the time, food poisoning is mild and goes away after a few days. All you can do is wait for your body to get rid of the germ that is causing the illness. But some types of food poisoning may be more serious, and you may need to see a doctor.
What are the symptoms?
The first symptom of food poisoning is usually diarrhea. You may also feel sick to your stomach, vomit, or have stomach cramps. Some food poisoning can cause a high fever and blood in your stool. How you feel when you have food poisoning mostly depends on how healthy you are and what germ is making you sick.
If you vomit or have diarrhea a lot, you can get dehydrated. Dehydration means that your body has lost too much fluid.
How do harmful germs get into food?
Germs can get into food when:
- Meat is processed. It is normal to find bacteria in the intestines of healthy animals that we use for food. Sometimes the bacteria get mixed up with the parts of those animals that we eat.
- The food is watered or washed. If the water used to irrigate or wash fresh fruits and vegetables has germs from animal manure or human sewage in it, those germs can get on the fruits and vegetables.
- The food is prepared. When someone who has germs on his or her hands touches the food, or if the food touches other food that has germs on it, the germs can spread. For example, if you use the same cutting board for chopping vegetables and preparing raw meat, germs from the raw meat can get on the vegetables.
How will you know if you have food poisoning?
Because most food poisoning is mild and goes away after a few days, most people don't go to the doctor. You can usually assume that you have food poisoning if other people who ate the same food also got sick.
If you think you have food poisoning, call your local health department to report it. This could help keep others from getting sick.
Call your doctor if you think you may have a serious illness. You may need to see your doctor if your diarrhea or vomiting is very bad or if you don't start to get better after a few days.
If you do go to the doctor, he or she will ask you about your symptoms (diarrhea, feeling sick to your stomach, or throwing up), ask about your health in general, and do a physical exam. Your doctor will ask about where you have been eating and whether anyone who ate the same foods is also sick. Sometimes the doctor will take stool or blood samples and have them tested.
How is it treated?
In most cases, food poisoning goes away on its own in 2 to 3 days. All you need to do is rest and get plenty of fluids to prevent dehydration from diarrhea. Drink a cup of water or rehydration drink (such as Pedialyte) each time you have a large, loose stool. Soda and fruit juices have too much sugar and shouldn't be used to rehydrate.
Antibiotics usually aren't used to treat food poisoning. Medicines that stop diarrhea (antidiarrheals) can be helpful, but they should not be given to infants or young children. You shouldn't take antidiarrheals if you have a high fever or have blood in the diarrhea, because they can make your illness worse.
If you think you are severely dehydrated, you may need to go to the hospital.
How can you prevent food poisoning?
You can prevent most cases of food poisoning with these simple steps:
- Clean. Wash your hands often and always before you touch food. Keep your knives, cutting boards, and counters clean. You can wash them with hot, soapy water, or put items in the dishwasher and use a disinfectant on your counter. Wash fresh fruits and vegetables.
- Separate. Keep germs from raw meat from getting on fruits, vegetables, and other foods. Put cooked meat on a clean platter, not back on the one that held the raw meat.
- Cook. Make sure that meat, chicken, fish, and eggs are fully cooked.
- Chill. Refrigerate leftovers right away. Don't leave cut fruits and vegetables at room temperature for a long time.
- When in doubt, throw it out. If you aren't sure if a food is safe, don't eat it.
Food poisoning is an illness caused by eating or drinking contaminated food. You can get food poisoning by eating food contaminated by harmful organisms, such as bacteria, parasites, and viruses.
The most common ways that harmful organisms are spread are:
- During food processing. It is normal to find bacteria in the intestines of healthy animals that we use for food. If bacteria come in contact with meat or poultry during processing, they can contaminate the food. Campylobacter, salmonella, and E. coli are often spread in this way. In one test, campylobacter was found in almost half of the raw chicken breasts tested.footnote 1
- During food growing. Fresh fruits and vegetables can be contaminated if they are washed or irrigated with water that is contaminated with animal manure or human sewage. Staph food poisoning, E. coli, and shigellosis are often spread through contaminated water.
- During food handling. Food can be contaminated when an infected person handles the food or if it comes in contact with another contaminated product. For example, if you use the same cutting board for both chopping vegetables and preparing raw meat, you risk contaminating the vegetables.
- Through the environment. Many harmful organisms that are commonly found in dirt, dust, and water can find their way into the foods we eat. These organisms include Clostridium perfringens and Cryptosporidium parvum. Environmental conditions—such as water polluted by farm runoff—may make this type of infection more frequent. Home-canned foods that have not been prepared properly may contain another organism, Clostridium botulinum.
The symptoms of food poisoning usually affect your stomach and intestines (gastrointestinal tract).
- The first symptom is usually diarrhea.
- Other symptoms include feeling sick to your stomach (nausea), vomiting, and abdominal (belly) cramps.
The time it takes for symptoms to appear, how severe the symptoms are, and how long the symptoms last depend on the infecting organism, your age, and your overall health.
The very young and the very old may be most affected by food poisoning. Their symptoms may last longer, and even the types of food poisoning that are typically mild can be life-threatening. This may also be true for pregnant women and people with impaired immune systems, such as those who have long-lasting (chronic) illnesses.
Not all food poisoning causes diarrhea, nausea, vomiting, and belly cramps. Some types of food poisoning have different or more severe symptoms. These can include weakness, numbness, confusion, or tingling of the face, hands, and feet.
Gastrointestinal symptoms, such as diarrhea and vomiting, can also be caused by organisms that aren't necessarily spread through food. These organisms are mainly spread through water or personal contact. Conditions caused by these organisms include infection with the parasite Giardia lamblia.
Learn more about specific food poisoning organisms, including how they are spread, their symptoms, and their treatment:
- Botulism ( Clostridium botulinum)
- Campylobacteriosis ( Campylobacter)
- C. perfringens food poisoning ( Clostridium perfringens)
- Hepatitis A
- Listeriosis ( Listeria monocytogenes)
- Marine toxins
- Salmonellosis ( Salmonella enterica)
- Shigellosis ( Shigella)
- Staph food poisoning ( Staphylococcus aureus)
- Toxoplasmosis ( Toxoplasma gondii)
- Vibrio vulnificus food poisoning
You may become ill with food poisoning after you eat food that contains bacteria, viruses, or other harmful organisms. Most cases of food poisoning follow the same general course.
After you eat a contaminated food, there is an hours-to-days delay before you notice symptoms. The contaminating organism passes through the stomach into the intestine, attaches to the intestinal walls, and begins to multiply. Some organisms stay in the intestine. Some produce a toxin that is absorbed into the bloodstream. And others directly invade body tissues. Your symptoms depend greatly on the type of organism that has infected you.
Different organisms cause similar symptoms, especially diarrhea, vomiting, and stomach cramps. Diarrhea and vomiting are a normal response as the body tries to rid itself of harmful organisms. Unless the illness is part of a recognized outbreak, it's difficult to identify the infecting organism. Lab tests usually aren't done.
In most cases, you recover in a few days to a week as toxins are flushed from your system. You may feel weak for several days after other symptoms go away.
Most of the time, food poisoning is mild and passes in a few days. But the symptoms and course of some types of food poisoning may be more severe. To learn more, see Symptoms for a list of specific organisms.
In rare cases, food poisoning can result in kidney or joint damage.footnote 2
What Increases Your Risk
People at increased risk of becoming ill with food poisoning and of having more severe symptoms include:
- Pregnant women.
- Young children.
- Older adults.
- People with an impaired immune system, such as people who have diabetes.
Things that increase your risk for getting food poisoning include:
- Eating or drinking unpasteurized juices, raw sprouts, unpasteurized milk, and milk products made from unpasteurized milk, such as certain soft cheeses.
- Eating raw or undercooked meat, poultry, eggs, fish, and shellfish (clams, oysters, scallops, and mussels).
- Eating or drinking food that has been contaminated through careless food processing or handling.
- Traveling to a developing country.
When should you call your doctor?
Call 911 or other emergency services right away if:
- You have signs of severe dehydration. These include little or no urine; sunken eyes, no tears, and a dry mouth and tongue; fast breathing and heartbeat; feeling very dizzy or lightheaded; and not feeling or acting alert.
- You think you may have food poisoning from a canned food and you have symptoms of botulism (blurred or double vision, trouble swallowing or breathing, and muscle weakness).
Call your doctor immediately if:
- You have severe diarrhea (large amounts of loose stool every 1 to 2 hours) that lasts longer than 2 days if you are an adult.
- You have vomiting that lasts longer than 1 day if you are an adult.
- You are pregnant and believe that you have been exposed to listeriosis or toxoplasmosis. To learn more, see the topic Toxoplasmosis During Pregnancy.
- You have sudden, severe belly pain.
Talk to your doctor if:
- You have symptoms of mild dehydration (dry mouth or passing only a little urine) that get worse even with home treatment.
- You have a fever.
- You aren't feeling better after 1 week of home treatment.
If you think you have eaten contaminated food, your local Poison Control Center can answer questions and provide information on what to do next. Poison Control Centers are usually listed with other emergency numbers in your telephone book.
Children, pregnant women, and people with long-lasting (chronic) conditions, such as diabetes, are more likely to have severe dehydration and should be watched closely for symptoms.
Watchful waiting is a period of time during which you and your doctor observe your symptoms or condition without using medical treatment.
Watchful waiting may be appropriate if you have diarrhea, stomach cramps, and other symptoms of stomach flu (gastroenteritis). Most people recover from these gastrointestinal illnesses at home in several days without medical treatment. Likewise, some cases of bacterial food poisoning are mild and pass in several days. But if diarrhea is severe or lasts longer than a week, call your doctor for advice.
Who to see
Health professionals who are able to diagnose and treat food poisoning include:
- Family medicine doctors.
- Primary care doctors.
- Physician assistants.
- Nurse practitioners.
You may be referred to a gastroenterologist if your symptoms are persistent or severe.
Exams and Tests
Most food poisoning is mild and passes in a few days, so most people don't go to a doctor for a diagnosis. You can often diagnose food poisoning yourself if others who ate the same food as you also become ill.
If you do go to your doctor, he or she will make the diagnosis based on your symptoms, a physical exam, and your medical history. Your doctor will ask where you have been eating and whether anyone who ate the same food has the same symptoms.
Sometimes the following tests are done:
- A stool culture may be done if your doctor suspects that you have eaten contaminated food, your symptoms are severe, or the diagnosis is uncertain.
- Blood tests may be done to help find out whether the food poisoning is caused by bacteria or to rule out other causes. A complete blood count and a chemistry screen can help show whether you are severely ill or dehydrated.
- If you are pregnant or have an impaired immune system and have been exposed to toxoplasmosis, you may need a toxoplasmosis test. To learn more, see the topic Toxoplasmosis During Pregnancy.
Your doctor may need to report your condition to the health department. This is done to help the government track the condition and identify possible outbreaks.
In most cases, the diarrhea and other symptoms of food poisoning go away in 2 to 3 days, and you don't need treatment. It may be longer than 2 to 3 days until you feel normal again.
All you have to do is manage symptoms, especially diarrhea, and avoid complications until the illness passes. In most cases, dehydration caused by diarrhea is the main complication.
Extra precautions should be taken to prevent dehydration in children.
To learn more about treating dehydration, including in children, see Home Treatment.
The goal of treatment is to replace fluids and electrolytes lost through vomiting and diarrhea. If dehydration is severe and can't be managed at home, you may need treatment in the hospital, where fluids and electrolytes may be given to you by inserting a needle into your vein (intravenously).
Medicines that stop diarrhea (such as Imodium) can help with your symptoms. But these medicines shouldn't be used in children or in people with a high fever or bloody diarrhea. Antibiotics are rarely used and only for certain types of food poisoning or in severe cases. Pregnant women with listeriosis or toxoplasmosis may receive antibiotics.
For more information on treatment for specific organisms, see Symptoms.
Botulism, E. coli infection, and infection during pregnancy
Pregnant women should always consult their doctors if they think they may have food poisoning, because the infection can be passed on to the fetus.
Toxoplasmosis and listeriosis can also harm your baby. If you are diagnosed with either of these conditions during pregnancy, you will be treated with antibiotics. To learn more, see Toxoplasmosis During Pregnancy.
You can prevent most cases of food poisoning by being careful when you prepare and store food. Wash your hands and working surfaces while preparing food, cook foods to safe temperatures, and refrigerate foods promptly. Be especially careful when you cook or heat perishable foods, such as eggs, meats, poultry, fish, shellfish, milk, and milk products. Also take extra care if you are pregnant, have an impaired immune system, or are preparing foods for children or older people.
The following steps can help prevent food poisoning (adapted from the U.S. Centers for Disease Control and Prevention).
- Shop safely . Bag raw meat, poultry, and fish separately from other food items. Young children can get sick from touching packaged poultry, so don't allow them to touch or play with packages of poultry in your grocery cart.
- Prepare foods safely . Wash your hands before and after handling food. Wash fruits, vegetables, and cutting boards. Follow procedures for safe home canning to avoid contamination.
- Store foods safely . Cook, refrigerate, or freeze meat, poultry, eggs, fish, and ready-to-eat foods within 2 hours. Make sure your refrigerator is set at 40°F (4°C) or colder.
- Cook foods safely . Use a clean meat thermometer to make sure that foods are cooked to a safe temperature. Reheat leftovers to at least 165°F (74°C). Don't eat undercooked hamburger. And be aware of the risk of food poisoning from raw fish (including sushi), clams, and oysters.
- Serve foods safely . Keep cooked hot foods hot [ 140°F (60°C) or above] and cold foods cold [ 40°F (4°C) or below].
- Follow labels on food packaging . These labels provide information about when to use the food and how to store it.
- When in doubt, throw it out. If you aren't sure if a food is safe, don't eat it. Reheating food that is contaminated won't make it safe. Don't taste suspicious food. It may smell and look fine but still may not be safe to eat.
- Make smart restaurant choices.
- Note the general cleanliness of the facility and staff. If you aren't confident that conditions are sanitary, leave.
- Restaurants are inspected by the local health department for cleanliness and proper kitchen procedures. Find out the inspection scores of selected restaurants. (They are sometimes posted in the restaurant.)
- Find out if food safety training is regularly provided for staff.
Many counties in the United States have extension services listed in the phone book. These services can answer your questions about safe home canning and food preparation.
To learn more, see Symptoms for a list of specific organisms.
Most cases of food poisoning will go away in a few days with rest and care at home. The following information will help you recover.
Dehydration is the most frequent complication of food poisoning. Older persons and children should take special precautions to prevent it.
To prevent dehydration, take frequent sips of a rehydration drink (such as Pedialyte). Try to drink a cup of water or rehydration drink for each large, loose stool you have. Sports drinks, soda pop, and fruit juices contain too much sugar and not enough of the important electrolytes that are lost during diarrhea, so they shouldn't be used to rehydrate. You can make your own rehydration drink.
Try to stay with your normal diet as much as possible. Eating your usual diet will help you to get enough nutrition.
Dehydration in children
Take extra precautions to prevent dehydration in children.
For children who are breastfeeding or bottle-feeding, continue the regular breast milk or formula feeding as much as possible. You may have to feed more often to replace lost fluids. Give an oral rehydration solution (ORS), such as Pedialyte, between feedings only if you see signs of dehydration.
For older children, give ½ cup [ 4 fl oz (118 mL)] to 1 cup [ 8 fl oz (237 mL)] of water, milk, or a rehydration drink each hour, and try to keep feeding your child his or her usual diet. Foods to try include potatoes, chicken breast without the skin, cereal, yogurt, and fresh fruits and vegetables. Try to avoid foods that have a lot of fat or sugar. Supplement feedings with small sips or spoonfuls of a rehydration drink or clear liquid every few minutes.
Medicines aren't used routinely in food poisoning. Medicines that stop diarrhea (antidiarrheals) can help with your symptoms. These medicines (such as Imodium) shouldn't be used if you have a fever or bloody diarrhea, because they can actually make you sicker. Don't give antidiarrheals to children.
Types of food poisoning that may be treated with medicines include:
- Botulism, which usually requires the botulism antitoxin and close medical care.
- Listeriosis, which in pregnant women is treated with antibiotics to prevent infection of the fetus or newborn. Babies with listeriosis may also receive antibiotics.
- Toxoplasmosis food poisoning, which in pregnant women is treated with antibiotics. To learn more, see the topic Toxoplasmosis During Pregnancy.
- Shigellosis, which may be treated with antibiotics. But some types of Shigella bacteria aren't killed by antibiotics. This is called resistance. Because using antibiotics can make these bacteria even more resistant, mild cases of shigellosis aren't usually treated with antibiotics.
- Centers for Disease Control and Prevention (2010). Campylobacter. Available online: http://www.cdc.gov/nczved/divisions/dfbmd/diseases/campylobacter.
- McGauly PL, Mahler SA (2011). Foodborne and waterborne diseases. In JE Tintinalli, ed., Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 7th ed., pp. 1062–1070. New York: McGraw-Hill.
Current as of: June 9, 2019
Author: Healthwise Staff
E. Gregory Thompson MD - Internal Medicine
Adam Husney MD - Family Medicine
Current as of: June 9, 2019