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Food Poisoning Symptoms causes Treatment & Preventions

Food poisoning is a common name given to Foodborne illness. The condition results from eating spoiled food. Spoilt food means the ingredients have become contaminated with disease-causing agents making the food toxic to consume.

Food poisoning is a common condition. According to the Center for Disease Control and Prevention, one out of every six U.S. adults falls prey to foodborne illnesses every year.

The causative factor of food poisoning can be anything; bacteria, viruses, or parasites. It is important to note that these disease-causing agents release toxins responsible for signs and symptoms such as nausea, vomiting, and diarrhea, some of the hallmarks of food poisoning.

Food Poisoning Symptoms causes Treatment & Preventions

Food can become contaminated at any stage of processing or production. The term is not solely applied to commercially prepared food. Homemade food can also be a source of foodborne illnesses due to improper handling or cooking methods.

Though typical, food poisoning is a severe condition and must be addressed vigilantly. Though the condition often presents with mild symptoms, the signs and symptoms become severe enough within no time to result in a fatal outcome. The condition is almost always better handled in a hospital setting.

Signs and symptoms of food poisoning

The signs and symptoms of food poisoning can hardly be overlooked. Their severity depends on the causative agent.

However, the length of time of appearance of earliest symptoms may vary. It may take 24 hours for some cases of food poisoning to be evident, while other pathogenic stimuli may trigger a response after 28 days.

Since the condition is associated with food intake, the signs and symptoms represent a disturbance in the gastrointestinal tract. For a case to be tagged as food poisoning, at least three of the following symptoms must be present in a person. These include;

  • Generalized abdominal pain and cramps
  • watery or bloody diarrhea
  • nausea
  • vomiting
  • loss of appetite
  • mild fever
  • weakness
  • headaches

The following symptoms indicate the condition has reached a potentially life-threatening threshold. These call for a hospital visit.

  • Frequent vomiting
  • Blood in vomit or stools
  • diarrhea lasting for more than three days despite home-based management
  • high-grade fever of more than 101.5°F (oral temperature)
  • extreme abdominal pain
  • extreme lethargy with difficulty communicating
  • symptoms of severe dehydration; dry mouth with excessive thirst, passing little to no urine, inability to keep fluids down, dizziness or lightheadedness
  • bloody urine
  • neurological signs and symptoms like blurry vision, muscle weakness and tingling in the arms and legs

Untreated and long-standing cases of food poisoning may result in;

  • Kidney failure
  • Chronic arthritis
  • Brain and nerve damage
  • Even death

Causes of food poisoning

Food reaches us after passing various stages. The various stages may vary depending on the food consumed; raw, fresh or canned and processed.

The chances of food contamination are always present, whether you are consuming homemade meals or dining out or take away options. 

The different production processes, which food goes through, include;

  • Growing
  • Harvesting
  • Processing
  • Storing
  • Shipping
  • Preparing

You may think that the fewer processes involved in food handling may mean fewer chances of food contamination. Well, think again.

This is not the case.

Food poisoning is often caused by cross-contamination. Cross-contamination transfers pathogenic agents from one surface to another, such as cutting knives or cutting boards to food being handled.

This is true in raw (chicken, meat) and ready-to-eat foods (some vegetables and salads). Cooking destroys disease-causing agents, and since these foods do not undergo cooking, they are more likely to carry harmful organisms that may cause food poisoning.

Here is a brief look into the different causative factors for food poisoning. 

  1. Bacterial agents

Bacterial contamination of food is the most prevalent culprit of all. According to the Center for Disease Control and Prevention, approximately 1,000,000 cases of food poisoning and about 20,000 hospital admissions are attributed to Salmonella infection every year, making it the most common of all bacterial causes of food poisoning.

Some of the common bacteria that cause food poisoning include;

  • E. coli
  • Listeria
  • Salmonella
  • Campylobacter
  • C. botulinum (that causes botulism)
Name of bacterium                     SourceFoods contaminated
Bacillus cereussoilcooked rice and pasta, meat products, vegetables
Campylobacter jejuniraw meat and poultryundercooked meat and poultry, raw milk and cross-contaminated food
Clostridium botulinum (very rare)soilfaulty processed canned meat and vegetables, cured meat and raw fish
Escherichia coli –the gut of humans and animalscontaminated water, milk, inadequately cooked meat, cross-contaminated foods
Listeria monocytogeneseverywheresoft cheeses, paté, pre-packed salad, cook-chill products
Salmonellathe gut of birds and mammals, including humans - spread by faeces into water and foodpoultry, eggs and raw egg products, vegetables
Staphylococcus aureusthe skin of animals and humanscured meat,  milk products, unrefrigerated, handled foods
  • Parasites

Parasitic food poisoning is rare. However, the infection caused by parasites is serious as they can reside in the gut for extended periods. High-risk individuals such as pregnant women, growing children, and weak immunity present with severe signs and symptoms.

Toxoplasmas is the most prevalent of all parasites to contaminate food. Some other parasites that may contaminate food include;

  • Giardia duodenalis or intestinalis
  • Cryptosporidium parvum
  • Cyclospora cayetanensis
  • Toxoplasma gondii
  • Trichinella spiralis
  • Taenia saginata/Taenia solium (Tapeworms)
Name of parasitesourceFood contaminated
Giardia duodenalis or intestinalisIntestines of animals and humansContaminated water, uncooked meat, cross-contamination
Cryptosporidium parvumintestines of many herd animals, contaminated soil, waterfood, water or cross-contamination
Cyclospora cayetanensisContaminated food and waterAny food and drink
Toxoplasma gondiiGut of catsRaw or undercooked food, untreated water,
Trichinella spiralisIntestine of animalsRaw or undercooked meat and wild game
Taenia saginata/Taenia solium (Tapeworms)Gut of humansRaw or undercooked infected beef or pork
  • Viral agents

Viruses are also common causes of food poisoning.  The most notorious of them is the norovirus or the Norwalk virus, responsible for over 19 million food poisoning cases per year.  

Some other viruses that cause food poisoning include;

  • Sapovirus
  • Rotavirus
  • Astrovirus
  • Hepatitis A virus
Name of virusSourceFood contaminated
Hepatitis AContaminated food and waterRaw or undercooked shellfish obtained from contaminated waters, raw produce, uncooked foods, and cooked foods not reheated after contact with an infected food handler
NorovirusContaminated food and waterProduce, shellfish, contaminated ready-to-eat foods

How contamination of food occurs?

As is evident from the sources mentioned above of contamination, food can become polluted from a wide range of sources. Microorganisms are present in all kinds of foods. Plastic wrapped foods like poultry or vegetables are not sterile, nor are raw meat, seafood, eggs, or poultry.

Cooking, washing and cleansing the food kills most of the pathogens. If food remains raw or undercooked, it can harbor disease-causing agents.

Cross-contamination of food can occur at any stage of handling and processing. Raw eggs and poultry, seafood can cross-contaminate safely cooked and ready to eat food products. Improper washing of fruits and vegetables may transfer parasite eggs.

Food handlers with poor personal hygiene may become the source of transmission. If nothing else, food poisoning can occur with improper washing of one’s hands before consuming food.

Who is at high risk of food poisoning?

The severity of food poisoning depends on

  • The type of infecting agent
  • Individual’s age
  • Health status
  • Extent of exposure

Certain people are at high risk of getting food poisoning. These include;

  • People over the age of sixty; as their immunity is weakened with age
  • Infants and young children; as they have partially developed immunity
  • Pregnant women; the hormonal and metabolic changes of pregnancy as well as the weakened immune system makes them more prone to food poisoning
  • Chronic disease patients; people with diabetes, HIV, liver disease or those receiving chemo or radiotherapy are at high risk of food poisoning
  • A person who undergoes a transplant and is on immunosuppressant therapy
  • Anyone on long term medications like steroids, antibiotics or antihistamines
  • Frequent travelers

Diagnosis of food poisoning

The diagnosis of food poisoning is based on the presenting signs and symptoms. Your doctor will take a detailed history and the duration of the signs and symptoms. Physical examination reveals any signs of dehydration if present.

Your doctor may call for

  • blood tests
  • stool culture
  • tests on food recently eaten

Treatment of food poisoning

Food poisoning usually resolves within three to five days with home-based remedies.

  • Preserving hydration should be the mainstay of home-based and hospital treatment. Sports drinks and beverages like Pedialyte, coconut water, and fruit changes help to restore the salt and water balance.
  • Take adequate rest and limit activity to prevent fatigue.
  • Some herbal teas that help soothe the irritant gut include chamomile, peppermint, and dandelion. 
  • Over-the-counter medications like Imodium and Pepto-Bismol should be taken after consulting with your doctor. These drugs stop nausea and vomiting, which act as compensating measures by the body to get rid of toxins. So taking these drugs may or may not be beneficial for a patient with food poisoning as they may mask the severity of the illness.
  • More severe cases of hydration may require hospitalization so that intravenous fluid therapy can be initiated.
  • Severe cases may also require antibiotics. Your doctor may prescribe antibiotics if the source of infection and the causative agent is known. This is especially important in pregnant cases diagnosed with listeria poisoning. Prompt treatment can help save the mother and child from unwanted complications.

Lifestyle and home remedies

While you are waiting for the symptoms of food poisoning to resolve, some home-based remedies can help you manage the condition. These include;

  • Drinking plenty of fluids. Use ice chips, clear soda, clear broth, non-caffeinated herbal drinks, teas, or sports drinks.
  • Consuming a light and bland diet to de-stress your digestive system. You may fast for few hours to give rest to your gut.
  • In the case of a breastfed child, the mother should continue nursing or using formula milk. 
  • Use oral rehydration solutions like Pedialyte or Enfalyte.
  • Add probiotics to your diet or take a supplement.
  • As symptoms improve, ease back into the regular intake of food. Start with bland, low-fat, easy-to-digest foods. For example, saltish crackers, bananas, rice pudding, oatmeal, chicken broth, blend potatoes, boiled vegetables, diluted fruit juices, etc.
  • Avoid dairy products, caffeine, alcohol, nicotine, and fatty or highly seasoned foods, sugar-laden foods, and spicy and fried items till your symptoms get better.

Complications of food poisoning

Most cases of food poisoning resolve by themselves. However, there are exceptions. People exposed to mushroom poisoning and botulism are more at risk of developing complications.

Some of the most common ones include;

  • Dehydration
  • Lactose intolerance
  • Anemia
  • Irritable bowel syndrome
  • Kidney failure
  • Hemolytic Uremic Syndrome
  • Reactive arthritis
  • Guillain-Barre syndrome
  • Pericarditis
  • Impaired absorption of drugs like oral contraceptives, antidiabetic and anti-epilepsy medications

The body reacts to food poisoning by flushing it outside the body via vomiting and diarrhea. The mucosal lining of the stomach and intestine increase water secreted into the intestinal lumen to flush the toxins away. There is a concomitant loss of essential salts and minerals with water.

This has no severe effect in healthy adults as the increased water secretion stimulates the thirst mechanism with resultant increased water intake.

However, excess water and salt loss can have severe repercussions on the elderly and children. Their bodies are slow to respond to the decreasing hydration levels. Children have smaller body surface areas and retain less water in their bodies.  Signs of dehydration are more apparent if the sudden water loss is not compensated at an equal speed. 

Some complications of food poisoning are associated with specific high-risk individuals. For example;

  • Complications of listeria food poisoning may be more pronounced for an unborn baby. Infection occurring in the first trimester may result in miscarriage, while in the last trimester, listeria infection can lead to outcomes like stillbirth, premature birth. 

A baby is born to a mother infected with listeria infection may have a potentially fatal infection after birth.

The complications may linger in the form of long term neurological damage and delayed development in Infants who survive a listeria infection.  

  • Certain Escherichia coli (E. coli) strains can cause hemolytic uremic syndrome, a serious condition.

The tiny blood vessels in the kidneys are damaged in this syndrome that may involve the whole kidney and result in kidney failure.


Food poisoning or foodborne illnesses are preventable. Here are some guidelines to be adopted as regular lifestyle habits to cut back any foodborne illnesses.

  • Maintain good personal hygiene. Wash your hands after every visit to the washroom. Washing your hands for at least twenty seconds is a must.  
  • Keep cooking utensils, and food surfaces clean and tidy. Use warm and soapy water to wash utensils, cutting boards and disinfect other surfaces you use.
  • Wash your hands with warm and soapy water before and after handling food.
  • Keep raw foods separate from ready-to-eat foods while you shop, prepare, and store to prevent cross-contamination.
  • Always cook foods thoroughly to a safe and appropriate internal temperature. Use a food thermometer to check your food is cooked correctly.
  • Keep the cooking temperature of ground beef to 160 F (71.1 C) and steaks, roasts and chops to at least 145 F (62.8 C). Cook chicken and turkey to a temperature of 165 F (73.9 C). Measure the temperature of the meat with a food thermometer. This should be done before removing meat from the heat source. Allow meat to rest for at least three minutes before serving it. It is better to cook meat at slightly higher temperatures than recommended.
  • Do not consume raw shellfish and other seafood. 
  • Promptly refrigerate or freeze perishable foods, ideally within two hours of purchasing or preparing them. In the summer heat, try to refrigerate perishable foods within one hour of buying.
  • Defrost food according to the retailer’s guidelines.
  • Reheat cooked food to 165 °F.
  • Never thaw food at room temperature. Always defrost it in the refrigerator or the microwave.
  • Cook any thawed food immediately. 
  • Throw out the food if you have any doubts about its preparing, handling, and storing. Food left at room temperature for an extended period too long may contain bacteria or toxins. Even if the food smells or looks OK, do not taste it.
  • High-risk individuals should be extra vigilant about their food intake. Caregivers should also take appropriate precautions while serving food.

Always be cautious while using foods like;

  • A Raw or rare meat and poultry
  • Undercooked or Raw seafood including shellfish (oysters, clams, mussels and scallops)
  • Raw or undercooked eggs
  • Foods containing eggs and cream as cookie dough and homemade ice cream
  • Unpasteurized juices and ciders
  • Raw, unwashed fruits and veggies
  • Unpasteurized milk and milk products
  • Cheese of all kinds
  • Refrigerated pates and meat spreads
  • Uncooked processed meat (hot dogs, luncheon meats and deli meats)
  • Sushi and other seafood that is consumed raw or undercooked

Handle food safely and avoid foods when in doubt. The temperatures between 40 °F and 140 °F are ideal for bacterial growth. Keep your food out of this risky zone by keeping cold food cold and hot food hot.

Abdur Rashid
Medically Reviewed By Abdur Rashid
MSC Public Health, MCSP, MHCPC
BSC (Hon) Physiotherapy
Consultant Neuro-spinal & Musculoskeletal Physiotherapist


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