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How do you know if your diarrhea is from food poisoning?

What is food poisoning?

Food poisoning, also called foodborne illness, is an illness that comes from eating contaminated food. It’s not caused by just the last thing you ate – it can take 1-3 days for symptoms to appear after eating contaminated food. The most common symptoms of food poisoning are diarrhea, vomiting, stomach cramps, nausea, fever, and dehydration. Food poisoning usually gets better on its own within a week.

What causes food poisoning?

Most cases of food poisoning come from bacteria, viruses, or parasites that contaminate food:

  • Salmonella – Raw poultry, eggs, beef, and sometimes vegetables and fruits can be contaminated with Salmonella bacteria. It takes 6-48 hours for symptoms to start.
  • E. coli – Raw and undercooked beef, raw milk, or contaminated vegetables and water can contain E. coli. Symptoms begin 3-4 days after exposure.
  • Listeria – Unpasteurized dairy products, deli meats, and ready-to-eat foods can be contaminated with Listeria bacteria. Symptoms start in 3 weeks after exposure.
  • Norovirus – Shellfish, fruit, vegetables, or water contaminated by norovirus particles causes symptoms 12-48 hours after exposure.
  • Campylobacter – Undercooked poultry often contains Campylobacter bacteria, causing diarrhea 2-5 days after ingestion.
  • Clostridium perfringens – Meats, poultry, or gravy can harbor C. perfringens bacteria and toxins. Symptoms start 6-24 hours after exposure.

In addition to bacteria, chemicals or toxins produced by bacteria can also cause food poisoning. Ciguatera poisoning comes from toxins produced by algae that accumulates in large reef fish. Scombroid poisoning is caused by toxins forming in some fish when not kept refrigerated properly after catching.

How do you know if it’s food poisoning versus other illnesses?

Diarrhea from food poisoning usually comes on faster and more severely than diarrhea from other causes. Other differences that point to food poisoning include:

  • Nausea, vomiting, abdominal cramps – Common with food poisoning, less frequent with infections or medication side effects.
  • Fever – More common with food poisoning than other diarrheal illnesses.
  • Recent restaurant meal or questionable food – If you remember eating risky foods recently, it’s more likely food poisoning.
  • Travel history – Foodborne infections are more common when visiting developing regions.
  • Timing of symptoms – Different bacteria have characteristic incubation times before symptoms start.
  • Sick contacts – Food poisoning often affects multiple people who shared a meal.
  • Duration under 1 week – Food poisoning symptoms typically resolve within several days to a week.

How is food poisoning diagnosed?

Doctors can diagnose food poisoning by:

  • Asking about your symptoms and recent food history
  • Sending stool samples to a lab to identify bacteria or toxins
  • Ordering blood tests looking for signs of infection

Identifying the specific germ is not always necessary. But lab tests can confirm food poisoning and identify treatment if the illness is severe or your symptoms don’t improve.

How to treat food poisoning

Here are some tips for treating food poisoning at home:

Rest and hydrate

Drink plenty of fluids to prevent dehydration. Water, fruit juice, herbal tea, broths, and electrolyte beverages help replace fluids lost from vomiting and diarrhea. Get extra rest to allow your immune system to fight the infection.

Eat bland, easy-to-digest foods

Once your nausea improves, eat small amounts of bland foods that are gentle on your stomach like crackers, toast, rice, bananas, or boiled potatoes. Avoid dairy, fatty, greasy, spicy or sugary foods until diarrhea stops.

Take over-the-counter medicines

Anti-diarrheal medications like loperamide (Imodium) and bismuth subsalicylate (Pepto-Bismol) can help control diarrhea episodes. Take ibuprofen, acetaminophen, or naproxen for fever, headaches, and body aches. Read labels carefully to avoid taking more than the recommended dose.

Prevent dehydration

Signs of dehydration include excessive thirst, dark urine, dizziness, and fatigue. Sports drinks and oral rehydration solutions help restore a balance of water, sugars, and electrolytes. Give children frequent sips and bites of fluids and bland foods.

Avoid certain foods and activities

Until symptoms end, avoid:

  • Solid foods high in fat, fiber, or spice which can make diarrhea worse
  • Caffeine and alcohol which promote dehydration
  • Dairy foods if you are lactose intolerant
  • Strenuous activity which can worsen nausea and fatigue

When to seek medical care

See your doctor if you have signs of dehydration, severe pain or illness, bloody stools, a weakened immune system, or if symptoms last more than 3 days. Seek emergency care for:

  • Bloody or black stools
  • No urine for 8 hours
  • Rapid heart rate, dizziness, confusion
  • High fever over 102°F
  • Persistent vomiting making it impossible to take fluids

Infants, young children, older adults, pregnant women, and those with chronic medical conditions have a higher risk of complications from food poisoning and require extra monitoring.

How long does food poisoning last?

Most cases of food poisoning resolve on their own within a week. How long symptoms last depends on:

  • The type of germ – Some viruses only cause 12 hours of symptoms while bacteria can cause illness over several days.
  • Your age and health – Children, pregnant women, older adults and those with weakened immune systems tend to have more severe, prolonged symptoms.
  • How much contaminated food was eaten – Large amounts of toxins or infectious germs can worsen the illness.
  • If treatment is received – Antibiotics may be used for certain bacterial infections and can shorten duration of illness if given early.

Here are typical durations of common foodborne infections:

Infection Usual Duration of Symptoms
Norovirus 12-60 hours
Salmonella 4-7 days
Campylobacter 2-5 days
E. coli 5-10 days
Listeria Variable, can be weeks

So in general, most food poisoning runs its course in under a week but severe cases can last longer. Call your doctor if symptoms don’t start improving after 3 days.

How to prevent food poisoning

You can reduce your chances of getting food poisoning by:

Practice safe food handling

  • Wash hands thoroughly with soap before and after handling food.
  • Sanitize kitchen surfaces, cutting boards, knives, counters.
  • Separate raw and cooked foods to avoid cross contamination.
  • Use separate plates and utensils for raw meat, poultry, fish, and eggs.
  • Cook food to proper temperatures high enough to kill germs.
  • Chill perishable foods within 2 hours and leftovers within 1 hour.
  • Check expiration dates and throw away food past its prime.

Avoid risky foods

  • Unpasteurized milk, cheese, juices, ciders
  • Raw or undercooked eggs, meat, poultry, fish
  • Unpasteurized honey
  • Raw sprouts like alfalfa
  • Soft cheeses unless they are clearly labeled as pasteurized
  • Deli meats, hot dogs, refrigerated pates or meat spreads
  • Food from salad bars, buffets, sidewalk vendors

Take extra care when eating out

Be cautious when dining at restaurants, cafeterias, fairs, street vendors, or anywhere else you aren’t sure about food handling practices. Watch out for cross contamination and improper cooking temperatures.


Diarrhea lasting over a day with nausea, vomiting, cramps, and fever suggests food poisoning. Seek medical attention for severe dehydration, bloody stools, high fever, or symptoms lasting more than 3 days. Most cases of food poisoning resolve within a week with rest and hydration. Prevent foodborne illnesses by practicing safe food preparation and avoiding risky foods.