Everything You Ever Wanted to Know About Food Poisoning

Food poisoning is a nasty illness to come down with, especially when it is serious and/or if you are away from home when it happens. You may encounter this disease when you eat or drink food or water that has been contaminated by viral, bacterial, or parasitic agents. Much of the time, food poisoning can be treated with home-care measures, but sometimes, medical intervention may be necessary. Read our definitive guide to food poisoning to learn how to diagnose, prevent, and treat food poisoning, wherever you happen to be on the globe.

Part I. Diagnosis and Treatment


It is important to understand the causes of food poisoning in order to gain an understanding of how to diagnose and treat the condition. Food may become contaminated anywhere in the production or preparation cycle, including farms, production plants, grocery stores, restaurants, and homes. Different types of food poisoning have different causes. Some common causes of food contamination that cause food poisoning are as follows:

  • Meat comes into contact with the animal’s intestinal bacteria or feces and is not cooked long enough to kill those germs
  • The water used to grow or prepare the food contains human or animal waste
  • The person who prepared the food did not wash their hands beforehand
  • The utensils, cutting surfaces, or other tools used to prepare the food are not clean
  • Foods are not stored in the proper conditions or are left too long in temperatures at which microorganisms can thrive

Foods that are especially vulnerable to the above contaminations and that commonly cause food poisoning are as follows:

  • Raw or undercooked fish, shellfish, meat, and eggs
  • Unpasteurized dairy, fruit juice and vegetables (the process of pasteurizing prevents contamination)
  • Foods containing mayonnaise (including potato salad and coleslaw) that are left out of the refrigerator too long
  • Frozen or refrigerated foods that are left out of the refrigerator too long or are improperly reheated
  • Home-canned foods or improperly canned commercial foods
  • Smoked or salted fish
  • Untreated drinking water, including well water and stream water

Common Symptoms

Food poisoning symptoms can range from mild or absent to severe; depending on the type and severity of the infection, you may have few or no symptoms, or you may experience life-threatening symptoms, such as severe dehydration or paralysis. Some common symptoms of food poisoning are as follows:

  • Intestinal discomfort or cramps
  • Nausea and vomiting
  • Headache
  • Fever and chills
  • Watery diarrhea (may be bloody)
  • Dizziness
  • Weakness
  • Dehydration

Symptom Checklist

Symptoms of some of the more common types of food poisoning are as follows. You are more likely to contract certain types of food poisoning when traveling in developing countries. Matching these symptoms against your own symptoms will help you and/or your doctor diagnose the type of food poisoning you are suffering from and determine a proper course of treatment.


  • Fever
  • Abdominal pain
  • Diarrhea
  • Nausea, and sometimes vomiting
  • Symptoms appear 1 to 3 days after consuming the contaminated food
  • You may have recently consumed meat, poultry, or egg yolks

E. Coli

  • Severe, sometimes bloody diarrhea is the main symptom
  • May also cause abdominal cramps, gas, fever, loss of appetite, or no symptoms
  • Rare symptoms include vomiting, pale skin, bloody or reduced amount of urine, bruising to the skin
  • Symptoms begin 1 to 8 days after consuming the contaminated food/water
  • Most infections associated with eating undercooked ground beef; can also be caused by consuming unpasteurized milk or apple cider, alfalfa sprouts, other contaminated foods, or contaminated water


  • Nausea and vomiting
  • Fever
  • Abdominal cramps
  • Bloody diarrhea
  • Onset of symptoms is 24 to 48 hours
  • You may have recently consumed seafood or raw, ready-to-eat produce


  • Diarrhea (may be bloody)
  • Nausea and vomiting
  • Abdominal pain and/or cramping
  • Fever
  • Malaise (general feeling of being unwell)
  • Symptoms start after 2 to 5 days
  • You may have recently consumed meat, poultry, unpasteurized milk or water from a questionable source


  • Diarrhea
  • Nausea
  • Fever
  • Muscle aches
  • Flu-like symptoms
  • If the infection spreads to the spinal cord and brain, symptoms may include stiff neck, headache, confusion, loss of balance and convulsions
  • You may be pregnant or elderly, take steroid medications, have a serious medical condition such as diabetes or kidney disease, or have a weakened immune system – these individuals are at a higher risk of contracting listeria than the general population
  • You may have within the past day or two consumed soft cheeses (e.g., crumbled blue cheese, feta), cold cuts, lunch meat, hot dogs, unpasteurized milk, or raw, unwashed vegetables
  • Symptoms start after 9 to 48 hours


  • Double vision
  • Blurred vision
  • Dry mouth
  • Difficulty swallowing
  • Muscle weakness
  • Slurred or slowed speech
  • Droopy eyelids
  • If left untreated, more severe symptoms such as paralysis of legs, arms, trunk and respiratory muscles may occur
  • Symptoms develop 18 to 36 hours after eating the contaminated food, but can occur as soon as six hours after or as late as 10 days later
  • You have recently consumed canned foods, chili peppers, tomatoes, garlic chopped in oil, fermented fish (such as sardines), potatoes baked in aluminum foil, or another food that was kept at a warm temperature for too long
  • In infants, symptoms may include constipation, lethargy, poor muscle tone, poor feeding habits and weak crying; consumption of honey may cause botulism in infants

Hepatitis A

  • Muscle aches
  • Loss of appetite
  • Headache
  • Fever
  • Weakness
  • Fatigue
  • Abdominal discomfort
  • Jaundice (after a few days)
  • You may be staying in or have within the last month traveled to a developing country
  • You may have in the last month consumed shellfish or raw produce or drunk water from a questionable source
  • Symptoms do not present themselves until 28 days after the initial infection (typically)


  • A large amount of watery diarrhea (may have a “fishy” odor)
  • Abdominal cramps
  • Dry mouth and skin
  • Excessive thirst
  • Nausea and vomiting
  • Low urine output
  • Unusual sleepiness
  • You may have recently consumed shellfish (especially raw oysters) or drinking water in a country where there is cholera – such as Africa, Asia, India, Mexico, or South or Central America

Fish tapeworm

  • You have eaten raw or undercooked freshwater fish
  • Symptoms may occur after several weeks, or you may not experience symptoms
  • If symptoms do occur, they may include weight loss, weakness, diarrhea, abdominal pain/discomfort, B-12 deficiency, and/or visible segments of worm in the stool

When to See a Doctor

In most cases, food poisoning symptoms are relatively mild (e.g., a small amount of vomiting or diarrhea) and will resolve on their own with self-care after a few days. However, if symptoms are severe or you have certain medical situations, it is imperative that you call a doctor right away. See a doctor if any of the following is true:

  • Your stools contain blood or pus
  • You have a fever higher than 101°F, or your child has a fever higher than 100.4°F in addition to diarrhea
  • You have signs of dehydration (dizziness, thirst, lightheadedness)
  • You have diarrhea and cannot keep down liquids because of vomiting or nausea
  • You have diarrhea after recently traveling to a foreign country
  • You have food poisoning after eating fish or mushrooms
  • You have symptoms of botulism
  • Diarrhea does not resolve after 5 days (2 days in a child or infant) or gets worse with time
  • You have noticed segments of worm in your stool
  • The infected person is very young or old, is pregnant, or has another serious medical condition
  • Your symptoms include a stiff neck or confusion

Food poisoning tests

To diagnose food poisoning, your doctor may, in some cases, simply consider your symptoms. The following tests may also be used to determine the infectious agent in your body that is causing your symptoms.

  • Blood tests
  • Stool culture test
  • Inspection of stool for parasites
  • Testing of the food that is potentially responsible for the poisoning

Medical treatments

 Medical treatments for food poisoning depend on the type and severity of the person’s condition and may include one or more the following:

  • Intravenous rehydration
  • Antibiotic treatment, such as tetracycline, cipro or doxycline
  • Antitoxin medication
  • Antiparasite medications, such as praziquantal or niclosamide
  • Antinausea and/or antidiarrheal medication
  • Enemas and/or induced vomiting
  • Vitamin B-12 injections (for parasites causing B-12 deficiency)
  • Hospitalization and intensive care (for severe illnesses, such as infant botulism)
  • Liver transplant (for severe Hepatitis A infection)
  • Poison antidotes, such as activated charcoal treatment

Alternative Diagnoses

In some cases, symptoms of another disease may mimic some common food poisoning symptoms, such as vomiting, diarrhea, abdominal pain, dizziness, and others. Some other conditions that cause certain food poisoning symptoms include the following:

  • Gastroenteritis (the “stomach flu”)
  • Lactose intolerance
  • Pregnancy
  • Severe anxiety
  • Crohn’s disease
  • Celiac disease
  • Drug overdose
  • Poisoning by another substance, e.g., carbon monoxide poisoning, poisoning from pesticides, household chemicals, or heavy metals