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.
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, your 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.
- Often 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.
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.
In rare cases, food poisoning can result in kidney or joint damage.
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 to Call a 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.
- You have sudden, severe belly pain.
Talk to your doctor if:
- You have symptoms of mild dehydration (dry mouth, dark urine, not much 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 at 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.
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.
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.
Botulism, E. coli infection, and infection during pregnancy
For botulism and some cases of E.coli poisoning, immediate and intensive medical care is usually needed.
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.
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 and 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. 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 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.
o Note the general cleanliness of the facility and staff. If you aren’t confident that conditions are sanitary, leave.
o 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.)
o Find out 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.
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 should be used to rehydrate.
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.