What Is Food Poisoning?

Food poisoning is common. In fact, according to the Centers for Disease Control and Prevention, every year approximately one in six individuals in the United States will have a foodborne illness.

Although the precise symptoms vary depending on the specific germ (e.g., bacteria, virus, or parasite) contaminating the food or drink, most people with food poisoning experience nausea, vomiting, and/or diarrhea that can be managed with at-home care measures. In some cases, antibiotics or hospitalization for intravenous (through the vein) fluids may be required.

Food Poisoning Symptoms

Most food poisoning illnesses cause nausea, vomiting, and/or diarrhea, which may be bloody, watery, or mucous-like.

Other potential symptoms of food poisoning include one or more of the following:

• Abdominal cramps and/or abdominal discomfort or pain
• Fever
• Headache
• Weakness

Symptoms may vary based on the specific germ contaminating the food. In addition, symptoms of food poisoning may develop within a few hours of eating or drinking, or they may take a longer period of time—even days—to develop.

When to Seek Medical Attention

Most cases of food poisoning are uncomfortable but pass without consequence. There are certain signs that indicate medical attention is needed, however.

Contact your healthcare provider if you:

• Cannot keep down liquids because of vomiting or you cannot (or feel as if you can't) drink enough to stay hydrated
• Become lightheaded or feel weak when you stand up
• Have a very dry mouth or throat
• Cannot urinate or urinate very little
• Experience diarrhea that persists for more than three days
• Have bloody or black, tarry stools
• Have a high or persistent fever
• Have sudden or severe abdominal pain, cramping, and/or abdominal rigidness
• Notice that your child cries without tears, has fewer wet diapers, dry mouth, or has any other symptoms of dehydration

Types of Food Poisoning

To better understand variations in how food poisoning can present, it's helpful to know about the various microbes that can cause it. Some common microbes include:

Norovirus

Norovirus can cause food poisoning and is often associated with cruise ships or other crowded settings, such as daycare centers.

Symptoms of norovirus food poisoning begin 12 to 48 hours after exposure and include abdominal cramps, along with watery diarrhea (more common in adults) and/or vomiting (more common in children).

Campylobacter

Food poisoning from Campylobacter is usually associated with eating undercooked chicken or drinking unpasteurized milk or contaminated water. Symptoms tend to develop two to five days after exposure and include diarrhea (sometimes bloody), fever, abdominal cramps, nausea, muscle aches, and headaches.

Guillain–Barré syndrome is a rare potential complication of Campylobacter infection.

Salmonella

Food poisoning from Salmonella causes watery diarrhea, fever, abdominal cramps, nausea, and vomiting six to 72 hours after exposure.

There are many potential food sources of salmonella, including eggs, chicken, meat, unpasteurized milk or juice, cheese, spices, nuts, and raw fruits and vegetables (notably, alfalfa sprouts and melon).

Escherichia coli O157

Individuals can develop an Escherichia coli (E. coli) O157 infection three to four days after eating contaminated, undercooked meat products, especially hamburgers. Other potential sources include raw milk, contaminated water, and unpasteurized juice.

Infection with E. coli O157 causes severe stomach cramps, bloody diarrhea, and, sometimes, a low-grade fever. While most people recover within five to seven days without treatment, a life-threatening condition called hemolytic uremic syndrome (HUS)—also called "hamburger disease"—may develop.

Shigella

Shigella is a bacteria that may cause bloody or mucous-containing diarrhea, in addition to abdominal cramps and a high fever, usually within one to two days of exposure.

Potential food sources of shigella contamination include raw vegetables, sandwiches, and salads that require a lot of preparation by hand, such as potato salad.

Clostridium Botulinum

Food poisoning from Clostridium botulinum, also called botulism, may occur after 12 to 36 hours of exposure to vegetables and other foods that are preserved and canned at home, such as honey (which is why it should not be fed to infants under 1 year of age).

In addition to nausea, vomiting, and abdominal cramps, botulism can cause neurological symptoms, some of which are potentially fatal (e.g., double vision and trouble with swallowing, talking, and breathing). In infants, weakness, constipation, and problems with feeding may occur.

Giardia Duodenalis

Infection with Giardia duodenalis, a parasite that can live in the intestines of animals and people, causes diarrhea, abdominal cramping, bloating, nausea, and foul-smelling stools within one to two weeks of exposure.

People usually get infected with Giardia duodenalis by drinking contaminated water; however, a person can also get infected by eating uncooked meat that is contaminated with the parasite's cysts.

Causes

The contamination of food may occur in different ways, such as food that is undercooked, improperly processed or canned, or prepared by someone who is sick.

Food grown in contaminated water is another potential source, as is cross-contamination that occurs during food preparation (for example, cutting up carrots on the meat cutting board).

While anyone can get food poisoning, certain groups are at a higher risk. Examples include:

• Anyone with a weakened immune system (for example, a person with HIV, cancer, liver disease, diabetes, or someone who is on steroid therapy)
• Pregnant women
• People who live in or spend a lot of time in crowded settings, like military barracks, daycare centers, cruise ships, or nursing homes

In addition, certain populations of people—infants, small children, and the elderly—are more likely to become dehydrated from food poisoning.

Diagnosis

Many people do not see their healthcare provider if they have classic food poisoning symptoms and there is a history of another person or group of people also getting sick from eating the same food.

This is generally reasonable unless you are a high-risk individual (e.g., elderly, pregnant or immunocompromised) or your symptoms are severe or persistent. In these instances, it's important to contact your healthcare provider.

If you see your healthcare provider, they will perform a medical history and physical examination. Additional tests (blood, urine, or stool tests, for example) may be ordered to evaluate for alternative diagnoses or complications and to look for the potential source of infection, especially in the case of a community outbreak.

Medical History

During a medical history, your healthcare provider will ask you several questions about your symptoms, including their duration and severity. They will also inquire about what you ate, as well as patterns of symptoms (e.g., whether or not everyone in your family got sick after eating a certain dish or after a family picnic).

Physical Examination

During the physical exam, your healthcare provider will check your blood pressure, heart rate, temperature, and weight. They will also press on your abdomen and listen to your bowel sounds to evaluate for diagnoses that may mimic that of food poisoning, like appendicitis.

Tests

In most cases, a healthcare provider will presume a diagnosis of food poisoning based on a medical history and physical examination alone. They are unlikely to move forward with further tests, since identifying the specific source of infection does not usually alter the treatment plan.

That said, additional tests may be ordered if your healthcare provider suspects a different diagnosis (for example, appendicitis) or a complication from food poisoning (for example, dehydration or sepsis from bacteria entering the bloodstream).

Examples of such tests include:

• A basic metabolic panel and a urinalysis to check for dehydration
• A complete blood count to check for severe infection or anemia
• A computed tomography scan to check for other diagnoses

Lastly, for outbreak identification or severe cases of food poisoning that may require a certain medication, stool tests may be ordered to look for and identify the cause of the infection.

Treatment

The key treatment for food poisoning is to stay hydrated, and this usually can be done effectively at home.

Hydration

To stay hydrated and replace the fluid you have lost, it's important to drink water that has salt and sugar in it.

You can breastfeed or use formula for babies and Pedialyte for children.

For adults or children, you can use an oral replacement therapy, such as Ceralyte or Oralyte, or you can make your own solution by adding 6 teaspoons of sugar and 0.5 teaspoons of salt to 1 liter of water. 

Avoid sports drinks like Gatorade, which cannot properly correct fluid and electrolyte losses because of their high sugar content. In fact, they may even worsen your diarrhea.

Medication

For the majority of cases of food poisoning, medications are not necessary.

Antibiotics are generally reserved for severe infections, such as shigellosis (Shigella infection). Another type of medication, called an antiparasitic, is used to treat food poisoning caused by parasites.

Anti-diarrheal agents, like Imodium (loperamide), are generally advised only for adults (not children) who have mild symptoms, no fever, and non-bloody diarrhea.

In some instances, your healthcare provider may recommend an anti-emetic such as Zofran (ondansetron) to suppress vomiting and prevent dehydration. The antacid Pepto-Bismol (bismuth subsalicylate) may also be recommended to ease uncomplicated diarrhea.

In severe cases of dehydration and/or in cases of food poisoning in high-risk individuals, such as the elderly, hospitalization for IV fluid delivery may be required.

Prevention

Avoiding contaminated foods and water is the key to preventing foodborne illnesses. That said, if you do get sick, don't be hard on yourself—sometimes, even with the best precautions, contamination occurs.

To reduce the chance of ingesting contaminated food:

• Wash your hands for 20 seconds with soap and water before, during, and after preparing and cooking food and before eating.
• Wash your knives, cutting boards, countertops, and other cooking utensils with soap and hot water.
• Rinse fresh fruits, vegetables, and bagged greens.
• Keep raw meat, eggs, seafood, and poultry away from other ready-to-serve foods or foods in the fridge.
• Use separate cooking utensils/plates for raw meat, poultry, and seafood.
• Avoid unpasteurized milk (raw milk) and juices.

Also, when cooking, use a food thermometer to make sure food is cooked to the appropriate temperature needed to kill germs (e.g., 165 degrees for all poultry).

In addition, throw out foods that are past their expiration date, even if they do not smell "bad" or look "funny." Many foods that are contaminated look and smell normal.

When traveling to other countries, do not drink tap water or use ice made from tap water, and try to avoid eating fruits and vegetables you can't cook or peel.

Another way to avoid food poisoning is to follow a predominantly plant-based diet, as many bacteria and parasites are more common in meat and animal products.

A Word From Verywell

Food poisoning happens. There are bacteria, parasites, and viruses that can spread from cooks to guests and from canned foods to family. You can protect yourself and your family by doing your best to safely prepare and cook your foods.

If you do get sick, give your body time to rest and, most importantly, drink ample fluids. Moreover, seek medical care or guidance if you are concerned about dehydration, or if you have worrisome, severe, or persistent symptoms.