Food Poisoning: What Causes It and How To Avoid It

An infectious disease expert shares the symptoms, treatment, and how you can protect yourself from foodborne illnesses.

A person washing their hands.

We’ve all had that unpleasant feeling of nausea and pangs from an upset stomach after eating.

While those symptoms can be a result of indigestion or a digestive condition, such as IBS, they could also be due to a foodborne illness. Every year, an estimated 1 in 6 people in the United States get food poisoning from ingesting food with harmful bacteria, parasites, or viruses, according to the Centers for Disease Control and Prevention.

Widespread foodborne illnesses are often linked to food contaminated during the farming or preparation process. Recently, dozens of people got sick from a listeria outbreak linked to cheese, and hundreds became ill from salmonella in cantaloupes.

Dr. Tina Z. Wang

“Many people have had some kind of gastrointestinal illness after encountering contaminated food, but for most who are healthy, with a strong immune system, it’s usually very mild to moderate and they get better on their own,” says Dr. Tina Z. Wang, who specializes in infectious diseases and hospital epidemiology at NewYork-Presbyterian/Columbia University Irving Medical Center. “There are general measures everyone can take, such as washing their hands before preparing and eating food, and being aware of any recalled items to prevent contact with contaminants.”

Dr. Wang shares more with Health Matters on what you need to know about food poisoning, including causes, symptoms, and how to treat yourself at home.

What causes food poisoning?
Dr. Wang: With a foodborne illness, or food poisoning, a foreign organism or toxin is introduced into your body. You start experiencing symptoms that are caused either by direct irritation of your gastrointestinal system from the harmful pathogen or from your body’s own response to expel it from your body.

There are several different types of pathogens that could cause illness, including bacteria, such as salmonella, E. coli, campylobacter, or listeria. There are also viruses — a common one is norovirus — and, more rarely, parasitic organisms.

They can contaminate food in different ways, usually during preparation. If somebody is ill and handling your food, they could potentially transfer the toxin from their hands onto surfaces and cooking tools or directly onto the food. If there’s contact between produce or salads with raw meats or poultry, that could be another direct way of contamination. If food is left out in an unrefrigerated setting, sometimes that can promote the growth of certain bacteria and toxins.

In larger-scale examples of produce contamination, what happens is the water used to irrigate fields or wash items can become contaminated with organisms and infect a larger quantity in bulk.

What are symptoms of food poisoning?
Symptoms can include:

  • Abdominal pain
  • Cramps
  • Diarrhea
  • Nausea
  • Vomiting
  • Lightheadedness
  • Fever
  • Fatigue

Symptoms can start as quickly as 30 minutes to an hour after being exposed, or they can start within a few days.

Who is at risk?
For most healthy adults, mild to moderate symptoms of foodborne illness will usually go away on their own. However, there is the potential for very severe illness, potentially even leading to death.

Those who are at higher risk of severe disease include:

  • People who are immunocompromised
  • Adults over 65
  • Children younger than 5
  • Pregnant women

How long does food poisoning last?
The duration of the illness depends on the organism that causes the food poisoning. Generally, symptoms from food poisoning can last from one day to about a week.

What is the treatment for food poisoning?
For most adults, the illness will resolve on its own. The main treatment is to hydrate and rest. Try to take in fluids like water or sports drinks with electrolytes. If you’re vomiting or having diarrhea, you want to be sure you’re replenishing your body.

Slowly ease your way back into eating, starting with foods that are blander and gentler on your gastrointestinal tract, like toast, rice, or bananas.

Stay away from things that could make your symptoms worse, like fatty and fried foods, or those that are very sugary, salty, or spicy.

Over-the-counter medicine can help, such as acetaminophen or ibuprofen for a fever, or anti-diarrheal medication.

When should you see a doctor?
If you’re experiencing very severe symptoms or fall into one of the high-risk groups, you should seek out a healthcare provider.

Warning signs to look out for include:

  • Very high or persistent fever
  • Severe abdominal pain
  • Bloody stool
  • Blood when vomiting
  • Difficulty keeping fluids down over a long period of time

If it’s been several days and you don’t feel like your symptoms are getting better, consult your doctor. There may be certain circumstances that require antibiotics, so you may require testing.

What’s the difference between the stomach flu and food poisoning?
Food poisoning can be an umbrella term that encompasses all foodborne illnesses, both viral and bacterial. Based on symptoms alone, there’s no definitive way to differentiate between bacterial or viral infections.

Norovirus, or the stomach flu, is the leading cause of foodborne illness in the United States, and is caused by a group of viruses that can lead to vomiting and diarrhea, among other symptoms. It can spread through contaminated food and water or between person to person through viral particles, including saliva, vomit, or stool.

Symptoms of bacterial and viral illnesses can be very similar, but ultimately the only way you can know for sure is through a stool test, which may be needed if symptoms don’t improve and become severe. If symptoms are mild, no tests are typically needed.

Tips To Prevent Food Poisoning

  • Wash your hands when preparing food, especially when handling raw meat or poultry.
  • Separate fresh fruit and vegetables from eggs, raw meat, poultry, or seafood.
  • Thoroughly cook food to a safe internal temperature.
  • Refrigerate leftover or perishable food within two hours of cooking.
  • Pay attention to public health announcements around recalled food.

Tina Wang, M.D. M.S., specializes in infectious diseases and is an associate hospital epidemiologist at NewYork-Presbyterian/Columbia University Irving Medical Center. In addition, she spends a portion of her time in the inpatient clinical service at both NewYork-Presbyterian/Columbia and NewYork-Presbyterian Allen Hospital. She completed her fellowship training at Weill Cornell Medicine, where she worked closely with the hospital epidemiology teams at NewYork-Presbyterian/Weill Cornell Medical Center and NewYork-Presbyterian/Columbia, before joining the Columbia Infectious Diseases Division and Infection Prevention and Control Department in 2020.

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