Overview of Food Poisoning

Young woman cracking egg over skillet on stove in kitchen

Caiaimage/Paul Bradbury/Getty Images 

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. While 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.

The diagnosis of food poisoning involves a medical history and physical examination. Stool tests are sometimes ordered to diagnose the specific germ causing the infection. Blood and urine tests may also be ordered to evaluate for dehydration.

Treatment of food poisoning usually entails simple self-care measures—most notably, drinking lots of fluids to prevent dehydration. Sometimes, antibiotics are prescribed to treat a bacterial infection. In severe cases, hospitalization for intravenous (through the vein) fluids may be required.

Symptoms

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

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

  • Abdominal cramps
  • Fever
  • Headache
  • Weakness

A potentially serious complication of all types of food poisoning is dehydration, which results from fluid loss from vomiting and diarrhea.

Besides slight symptom differences based on the specific germ contaminating the food, the timing of symptoms may also vary. In other words, symptoms of food poisoning may develop within hours of eating or drinking, or they may take time, even days, to develop.

To provide a better understanding of this time and symptom variation, here are several examples of the germs that may cause food poisoning:

Salmonella

Food poisoning from Salmonella causes watery diarrhea, fever, abdominal cramps, nausea, and vomiting about 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).

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 three days of exposure. Potential foods sources for shigella contamination include raw vegetables, sandwiches, and salads that involve a lot of hand preparation, such as potato salad.

Campylobacter

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

Escherichia coli 0157

Individuals can develop an Escherichia coli (E. coli) O157 infection about one to 10 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.

Clostridium Botulinum

Food poisoning from Clostridium botulinum, also called botulism, may occur with exposure to vegetables and other foods that are preserved and canned at home, such as honey (which is why infants aren't supposed to eat honey).

In addition to nausea, vomiting, and abdominal cramps, botulism can cause neurological, potentially fatal symptoms, such as double vision, and trouble with swallowing, talking, and breathing. In infants, weakness, constipation, and problems with feeding may occur.

Norovirus

Norovirus can cause food poisoning and is often associated with cruise ships or other crowded settings like daycare centers. Symptoms of norovirus food poisoning begin about 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).

Giardia duodenalis

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

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

Causes and Risk Factors

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 when cross-contamination occurs during food preparation (for example, cutting up carrots on the meat cutting board).

It's important to note as well, while anyone can get food poisoning, certain populations of people are at a higher risk. Examples of such populations include:

  • Anyone with a weakened immune system (for example, a person with HIV, cancer, liver disease, diabetes, or someone who is on steroid therapy)
  • People with specific medical conditions (for example, people with low stomach acid or iron overload are more likely to get an infection from the bacteria, Vibrio vulnificus)
  • Pregnant women
  • People who live in or spend a lot of time in crowded settings, like military barracks, day care 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

While food poisoning can be tricky to diagnose because there are so many potential sources of infection, a thorough medical history and physical examination are usually all that is needed. Sometimes, for more serious cases, or to evaluate for alternative diagnoses or complications, blood, urine, or stool tests may be utilized.

Medical History

During the medical history, your doctor will ask you several questions about your symptoms, including their duration and severity. He may also inquire about your pattern of symptoms, like 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 doctor will check your blood pressure, heart rate, temperature, and weight. He 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

Depending on your medical history and physical exam, your doctor may order various tests. For instance, to evaluate for dehydration a blood test called a basic metabolic panel (BMP) and a urinalysis may be ordered. Likewise, to check for a severe infection or anemia, a complete blood count (CBC) may be ordered.

Lastly, depending on your doctor's underlying suspicion, stool tests to look for bacteria, like salmonella or shigella, or the parasite, Giardia duodenalis, may be ordered.

Treatment

The key treatment of food poisoning is to stay hydrated, which can usually be done at home.

Hydration

To stay hydrated, 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, you can buy packets of Oral Replacement Serum or Therapy (ORS or ORT) to add to water, or you can add 6 teaspoons of sugar and 0.5 teaspoons of salt to 1 Liter of water

Medication

For the majority of cases of food poisoning, medication, such as antibiotics, are not necessary. Instead, antibiotics are generally reserved for severe infections, like shigellosis (a 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 only advised for adults (not children) who have no fever and non-bloody diarrhea.

Important Point

Be sure to only take an anti-diarrheal drug under the guidance of your doctor.

When to See Medical Attention

While most cases of food poisoning can be managed at home with fluid intake, certain signs indicate that medical attention is needed.

In these cases, medication or even hospitalization for intravenous fluids may be warranted.

Here are some signs to watch out for:

  • Cannot keep down liquids because of vomiting or will not/cannot drink enough to stay hydrated
  • Have bloody or black, tarry stools
  • Become lightheaded when standing up or feeling weak
  • Cannot urinate or urinates very little
  • Have a high or persistent fever
  • Have severe abdominal pain, cramping, and/or abdominal rigidness
  • Become weak or tingly, especially in the legs, or have blurry vision or problems breathing. (This can be concerning for a disease called Guillain–Barré syndrome, which is a rare potential complication of Campylobacter infection).
  • If your child cries without tears, has fewer wet diapers, dry mouth, or has any other symptoms of dehydration

Seek Emergency Care

You may need to go directly to the hospital or call 911 if you or someone you are caring for is very sick. For instance, if someone is not responding, is vomiting red blood, or is too dehydrated to sit up and cannot drink, call for immediate medical attention.

Prevention

Avoiding contaminated foods 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.

Here are some key tips for reducing your chances of ingesting contaminated food:

  • Wash your hands for 20 seconds with soap and water, before, during, and after preparing/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, be sure to use a food thermometer to ensure your food is cooked to the appropriate temperature needed to kill germs. (e.g., 165°F for all poultry).

In addition, remember to 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.

Summer Tip

Since bacteria multiply faster in warmer temperatures, cases of food poisoning increase in the summer months—so, be extra careful to follow food safety rules during summer picnics and barbeques.

A Word From Verywell

Food poisoning happens. There are bacteria, parasites, and viruses that can spread from cooks to guests and canned foods to family. In the end, do your best to protect yourself and your family by safely preparing and cooking your foods.

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

Was this page helpful?

Article Sources