What is food poisoning?

Food poisoning, also known as foodborne illness, are the symptoms that people experience after eating or drinking something that has been contaminated by germs, bacteria, or other toxins. These symptoms include diarrhea, nausea, stomach pain, vomiting, headaches, and even fevers. These symptoms are typically mild and go away on their own after 1-3 days, though some cases may last up to a week. However, more serious episodes of food poisoning can lead to complications like severe infection that require a visit to the doctor or hospitalization.

How does it happen?

The food we eat can be contaminated in many different ways. For example, bacteria can grow in food when it is not fresh, properly cleaned, or undercooked. It can also happen when perishable foods like meat, dairy, or salads are left to sit at room temperature instead of being stored in the refrigerator.

Some foods, like fruits and vegetables, can become contaminated if they are not thoroughly washed. Other contaminants can happen when people do not wash their hands when preparing food or through cross contamination. For example, using a cutting board or utensils to prepare raw meat and then using them again to prepare ready to eat foods like salads or fruits without washing them thoroughly.

Food poisoning is also very common when traveling. When traveling to new countries, they may have different sanitation practices than we are used to, which can contribute to something called traveler’s diarrhea.

Common causes

As the name suggests, foodborne illness usually occurs after eating contaminated food. Common causes of these foodborne illnesses are pathogens such as salmonella, E. coli, or listeria, or hepatitis A. These pathogens are found in common everyday foods:

Common pathogens Common Sources
Norovirus Undercooked shellfish, leafy greens, fresh fruits, and person-to-person contact
Salmonella Raw eggs and undercooked poultry
E. Coli Undercooked meat and raw vegetables
Listeria Cheeses, raw sprouts, deli meats, and hot dogs
Hepatitis A Shellfish, fresh produce, or water and ice contaminated by fecal matter (human waste).
Campylobacter Undercooked poultry, contaminated vegetables, and raw milk
Shigella Cream or mayonnaise-based salads like tuna, potato, macaroni or chicken salad
Is food poisoning contagious?

Yes, food poisoning can be contagious. Foodborne illness is mainly caused by eating contaminated food. In some cases, it can pass between people, like direct contact with an infected person’s hands or bodily fluids.  Outbreaks can occur in shared spaces such as cruise ships, dormitories, and hotels, particularly with highly contagious pathogens like norovirus. Good hand hygiene and sanitation practices significantly reduce these risks.

Additionally, some pathogens spread between people more easily than others. For example, norovirus, one of the most common causes of stomach flu, spreads early through close contact, contaminated surfaces, or food. It is linked to ~50% of cases of foodborne illness in the United States. Other bacteria, such as Salmonella and Campylobacter, are more often linked to eating contaminated food rather than spreading directly from person to person.

Management
  • OTC medication: In adults, mild symptoms of food poisoning can be managed with some over the counter medications. However, these medications will only provide relief – they will not treat the underlying cause. But in mild cases, relief of these symptoms is enough to keep us comfortable enough while the illness runs its course.
    • Fluids –> First line management strategy
      • Fluids are helpful for preventing dehydration by replacing the volume lost from vomiting and diarrhea. It is best to sip clear liquids, and some oral rehydration solutions are available like Pedialyte. When selecting fluids to prevent dehydration, it is best to avoid dairy, caffeine, and sugary drinks.
      • Helpful tip: if you are experiencing vomiting, try starting with a small amount and increasing as tolerated.
    • Loperamide (Imodium)
      • Loperamide is an antidiarrheal medication that is available over the counter and provides relief to symptoms of food poisoning.
      • How to take it: For adults, It is dosed at 4 mg by mouth initially, then 2 mg by mouth for every loose stool thereafter. Max daily dose of 8 mg in one day.
      • Side effects: Loperamide is generally well tolerated, but common side effects can include constipation, dizziness, nausea, or abdominal cramping.
      • WARNING: it is important to avoid loperamide if your symptoms include a fever, bloody/black tarry stools, or severe abdominal pain.
    • Bismuth Subsalicylate (Pepto Bismol)
      • Pepto Bismol is another antidiarrheal medication available over the counter. However, Pepto Bismol may also help relieve additional symptoms like nausea, vomiting, and stomach cramps.
      • How to take it: For adults, Pepto Bismol is available as both liquid or capsules. The liquid formula is dosed 30 mL by mouth every 30-60 minutes with a maximum daily dose of 240 mL. The capsules are two 262 mg capsules by mouth every 30 minutes with a maximum daily dose of 16 capsules.
      • Pepto Bismol can cause constipation and discoloration of the tongue and stool. Your tongue and stool can become black. This is a harmless side effect and should return to normal after you stop taking the medication
When to seek help

Most instances of food poisoning are mild. It can look like diarrhea, occasional and manageable vomiting, or stomach upset. These milder episodes also tend to go away on their own after 1-3 days and can be self-managed with over-the-counter products like those mentioned above.

However, sometimes these symptoms can become serious. You should see a doctor if your symptoms become more severe. These severe symptoms can include but are not limited to:

  • Blood in the stool
  • Fever over 101.3ºF or 38.8ºC
  • Vomiting so severe that you cannot keep any liquids down
  • Signs of severe dehydration (not enough water in your body) like dizziness, confusion, or you are unable to pee
  • If symptoms persist beyond 5 days

At Risk Populations: Certain groups of people are also at higher risk of severe food poisoning complications. These include young children, older adults, pregnant people, and people with weakened immune systems. These individuals may become seriously ill more quickly and should seek medical care sooner if symptoms are severe or persistent.

More severe cases of food poisoning may require prescription medications such as ondansetron to help control nausea and vomiting. Antibiotics may not be necessary, especially if symptoms begin to improve or if foodborne illness is caused by a virus.  However, they may be prescribed in certain situations like severe cases of traveler’s diarrhea, or if a patient is at a higher risk for developing complications.

Prepared By Jester Kyle Calalang PharmD Candidate 2026

References

Switaj TL, Winter KJ, Christensen SR. Diagnosis and Management of Foodborne Illness. Am Fam Physician. 2015;92(5):358-365.

Centers for Disease Control and Prevention. Preventing Food Poisoning. Published November 24, 2025. Accessed April 19, 2026. https://www.cdc.gov/food-safety/prevention/index.html

Mayo Clinic Staff. Food poisoning (foodborne illness): Symptoms and causes. Published August 16, 2025. Accessed April 19, 2026. https://www.mayoclinic.org/diseases-conditions/food-poisoning/symptoms-causes/syc-20356230

Cleveland Clinic. Food Poisoning: Symptoms, How You Get It & Treatment. Updated May 28, 2025. Accessed April 19, 2026. https://my.clevelandclinic.org/health/diseases/21167-food-poisoning