Food Poisoning – Symptoms, Causes and Treatment


Food poisoning is caused by bacteria, viruses and other parasites. The illness usually lasts for 4–7 days.

Food Poisoning – Symptoms, Causes and Treatment

Food poisoning, or Gastroenteritis is illness caused by eating contaminated food. Bacteria, viruses and parasites or their toxins present in the food are the main causes of food poisoning.

The presence of infectious organisms in food can occur in any processing or manufacturing industry. Foods cooked at home can also cause contamination if it’s incorrectly handled.

Vomiting, diarrhea, nausea, or bloating is the common food poisoning symptoms that can start within hours of consuming contaminated food. In most cases, food poisoning resolves without treatment. However, if the condition becomes serious, you must get the right medical treatment.

How is food contaminated?

The contamination of food can occur at any stage during the production, processing, or cooking process. For example:

  • Not cooking food thoroughly (particularly meat)
  • Leaving cooked food at warm temperatures for too long
  • Not reheating stored food
  • Eating food that has passed its “use by” date

Foods that can be easily contaminated (if not stored properly) include:

  • Raw meat and poultry
  • Raw eggs
  • Raw sea foods
  • Unpasteurised milk
  • “Ready-to-eat” foods, soft cheeses and pre-packed sandwiches


Food poisoning is also called a foodborne illness. The common bacterial strains pathogenic to humans are Bacillus cereus, Campylobacter jejuni, Clostridium botulinum, Clostridium perfringens, Cronobacter sakazakii, Escherichia coli, Listeria monocytogenes, Salmonella spp., Shigella spp., Staphylococcus aureus, Vibrio spp. and Yersinia enterocolitica.  

The viral strains include Hepatitis A and Noroviruses. The parasites are yclospora cayetanensis, Toxoplasma gondii and Trichinella spiralis. 

According to Hippocrates, there is a powerful connection between our food and our illness. Food pathogens are biological agents that cause disease when they are ingested. 

A foodborne disease outbreak happens when a common symptom occurs for a group of people ingesting the same food. 

Food poisoning occurs when the ingested pathogen, along with the food, establishes itself, grows and multiplies inside the human host. 

Foodborne illness is divided into two types foodborne infection and foodborne intoxication. 

A foodborne infection is caused when you consume foods contaminated by pathogens like viruses, bacteria or parasites. A foodborne disease leads to inflammation of the bowels and stomach. It also causes diarrhoea, vomiting, fever, abdominal pain, cramps and nausea. 

A food intoxication occurs when you consume foods that contain toxins or pathogens. For example, Clostridium botulinum produces harmful bacteriocin. These bacteriocins, when ingested, can cause illness. At times, these bacteriocins can be fatal. 

Some of the common organism that causes food poisoning, their symptoms and their onset time are listed below.

Organism or toxin

Onset time to symptoms


Bacillus cereus (Emetic toxin).

8–16 hours. The symptoms are set within 2–4 hours if the toxin is predominant.

Abdominal pain, abdominal cramps, nausea and vomiting.

Staphylococcus aureus and its enterotoxins

1–7 hours. On an average of 2–4 hours, the symptoms set in

Vomiting, nausea, diarrhoea, abdominal pain and prostration.

Clostridium perfringens

2–36 hours. The average time is 6–12 hours.

Diarrhoea, putrefactive diarrhoea, abdominal cramps, nausea and vomiting.


12–48 hours.

Vomiting, nausea, dehydration and watery, non-bloody diarrhoea.

Salmonella spp., Shigella spp., E. coli

6–96 hours. The mean time is usually 6-12 hours.

Abdominal cramps, fever, diarrhoea, headache, nausea and vomiting.

Vibrio cholerae, Vibrio parahaemolyticus

6 hours to 5 days.

Diarrhoea, vomiting, abdominal cramps, fever, nausea, malaise, dehydration and headache.

Enterohaemorrhagic E. coli, Campylobacter spp.

1–10 days.

Bloody diarrhoea, nausea and vomiting, fever, abdominal pain and malaise.

Rotavirus, Astrovirus, enteric Adenovirus

3–5 days.

Vomiting, fever and non-inflammatory diarrhoea.

Yersinia enterocolitica

3–7 days.

Fever, abdominal pain and diarrhoea.

Entamoeba histolytica

1 to several weeks.

Diarrhoea, abdominal pain, headache, constipation, ulcers and drowsiness. It is often asymptomatic.

Taenia saginata, Taenia solium

3–6 months.

Insomnia, nervousness, anorexia (loss of appetite), weight loss, abdominal pain, gastroenteritis and hunger pain.

Clostridium botulinum and its neurotoxins.

2 hours–6 days. The average mean time is 13–36 hours.

Double or blurred vision, vertigo, difficulty swallowing, loss of reflux or light reflux, weakness, dry mouth and respiratory paralysis.

Trichinella spiralis

4–28 days.

Fever, gastroenteritis, oedema around the eyes, muscular pain, perspiration, laboured breathing and prostration.

Salmonella Tympi

7–28 days.

Headache, fever, cough, nausea, vomiting, chills, abdominal pain, bloody stools, rose spots, constipation and malaise.

Toxoplasma gondii

10–13 days.

Headache, fever, rash and myalgia.

Listeria monocytogenes and Campylobacter jejuni

The period varies.

Chills, fever, headache, prostration, malaise and swollen lymph nodes.

Causes of Food Poisoning

With reference to a report published by EverydayHealth, the main causes of food poisoning are listed as follows:

1. Salmonella

Most people are familiar with the term salmonella, but they may not know that there are more than 2,000 different types of the bug. It’s usually associated with animal products like chicken, eggs, and milk, but raw vegetables and even water can carry salmonella, too.

Salmonella is usually introduced to foods at a processing plant or when the foods are handled.

“Symptoms of salmonellosis vary from a mild gastroenteritis to more severe and prolonged diarrhea,” says Kristina D. Mena, PhD, regional dean of the UT Health School of Public Health in El Paso.

Moreover, in salmonella infection, the symptoms of food poisoning start after 48 to 72 hours.


coli was commonly associated with undercooked foods. Symptoms can include nausea and vomiting, watery diarrhea, or sometimes bloody diarrhea, depending on the E. coli type.


Campylobacter is most commonly identified in the United States and Europe. This bacterium may also cause high fever, arthritis, and Guillain-Barré syndrome [severe, progressive muscle weakness].


Food poisoning is not only caused by meats, but also vegetables. Shigella is transmitted via vegetables, due to unhygienic production process. Studies also prove that flies may have a role in its transmission. Symptoms of Shigella typically include abdominal cramps and bloody stools.


Listeria can be seen in raw, unpasteurized milks and cheese; ice cream; and raw or undercooked poultry and seafood. Similar to other food-borne illnesses, a listeria infection can cause diarrhea and fever. These infections can be especially dangerous for pregnant women and can lead to stillbirth, miscarriage, premature birth, or life-threatening infection to the newborn.

6.Enteric Viruses

Viruses like norovirus and hepatitis A stand as the most common causes of food poisoning. Under norovirus, people can experience vomiting. Infections caused due to Hepatitis A may result in nausea, malaise, and jaundice. These symptoms are common in older people.

Major Symptoms

Some  common symptoms of food poisoning include diarrhea, vomiting, upset stomach and nausea. However, these symptoms can differ for every individual.You must immediately consult a doctor if you have severe symptoms such as:

  • Diarrhea and a fever higher than 102°F
  • Bloody diarrhea
  • Extreme vomiting
  • Dehydration causes signs such as dry mouth and throat, dizziness and not urinating (peeing) much

People who are at high risk of food poisoning

Anyone can get food poisoning, but a certain group of people are more prone to such serious illness. Their ability to fight infections may not be effective. Thus, people who are having regular signs for food poisoning might fall under the following category:

  • Adults aged 65 and older
  • Children younger than age 5
  • People whose immune systems are weakened by health conditions or medicines

Diagnosis and Treatment

Food poisoning is a common ailment that occurs when you eat unhealthy/improperly cooked foods. Upon diagnosis, the doctor may ask you for a detailed history, including how long you’ve been sick, your symptoms and specific foods you’ve eaten before falling sick. The doctor may also look out for signs of dehydration.

Based on your symptoms, the doctor may conduct certain diagnostic tests, such as a blood test and stool culture, to identify the cause of the illness. However, in some cases, the cause of food poisoning cannot be identified.

Treatment for food poisoning depends on the severity of your symptoms. Most people get cured without treatment within a few days, while some go through a tougher phase. Treatment of food poisoning may include:

  • Replacing lost fluids in the body – Minerals such as sodium, potassium and calcium that maintain the balance of fluids in your body which may be lost due to diarrhea, need to be replaced. Some children and adults with severe diarrhea or vomiting may need hospitalisation, where they can receive salts and fluids through an IV (intravenously). This prevents them from dehydration.
  • Antibiotics -Your doctor may prescribe antibiotics if you have a food poisoning due to bacteria. For example: Food poison due to Listeria needs to be treated with IV antibiotics during hospitalisation. During pregnancy, antibiotic treatment may help keep the infection from affecting the baby. Even though it is one of the common treatment ways, antibiotics will not help in all conditions. You can talk to your doctor about the alternative ways.
  • Wash hands regularly– Food poisoning can also occur due to poor hygiene. Make sure you wash your hands before and after eating. Do not prepare or eat food and drinks with an unwashed hand. Avoid coughing or sneezing into your hands while preparing food. Such small precautions can prevent you from having food poisoning.

Home Remedies for food poisoning

There are high chances for food poisoning to get cured within 48 hours. You may not always depend on a doctor, but you can gradually it by yourself at home. The following are some of the effective home remedies for food poisoning.

  • Avoid solid intake for a few hours.
  • Try taking small sips of water at regular intervals.You can also try drinking clear soda, clear broth. In case you have severe dehydration or diarrhea, you can take Electral Powder – a WHO-based ORS (Oral Rehydration Salt) formula. Meanwhile, make sure your urine is clear and not dark.
  • Gradually, you can start eating low-fat, easy-to-digest foods. Avoid intakes if your nausea returns.
  • Avoid dairy products, caffeine, alcohol and other fatty or highly seasoned foods.
  • Dehydration can easily make you feel tired. Make sure you have enough rest during such times.

Diagnosis of Food Poisoning  

 Diagnostic Test 

Diagnostic tests are used to identify the condition of the disease and its underlying cause. Usually, a blood test is preferred for food poisoning to determine the presence of any parasites.   

A physical test is also performed for food poisoning. Blood pressure and pulse are also checked to identify any signs of dehydration. The body temperature is detected for any fever symptoms. 

A stool test is performed to identify any signs of virus or bacteria. Your doctor will give the instruction for a stool test. And the stool sample by the patient should be sent, and the sample will be tested for the presence of any bacteria or parasites. 

Blood Test 

Blood culture determines any pathogen growth in your blood, like Salmonella typhi. 

A blood test will help identify the infection and detect if you have any dehydration. 

Treatment of Food Poisoning 

Stay Hydrated 

 drinking water

If you have food poisoning, the primary side effect will be dehydration. It is essential for you to keep yourself hydrated to avoid dehydration. Dehydration does not mean you lose water but also your electrolytes, so always remember to keep yourself hydrated. 

Take over-the-counter (OTC) medications. 

Medication can help with symptoms and reduce their severity when you have food poisoning. The first aid for food poisoning will be to restore the lost electrolytes. There are many electrolyte powders available to restore lost electrolytes. 

Supplementary foods and powders may help with dehydration and weakness caused due to food poisoning. Over-the-counter drugs like loperamide and bismuth subsalicylate are usually used to treat food poisoning. 

These drugs will help to reduce the severity of the symptoms. Loperamide will help to reduce the frequency of diarrhoea. However, loperamide will not work for bloody stools, mucus in stools and fever. This drug can be life-threatening if it is taken above the recommended dose. It can cause side effects like fatigue and constipation. 

Bismuth subsalicylate is used for heartburn, diarrhoea and stomach upset. These are recommended for those above the age of 12 and above. Bismuth subsalicylate is placed under the category of anti-diarrhoeal agents. 

The drug works by reducing the fluid flow in the bowel and inflammation of the intestine. Bismuth subsalicylate kills the organism that causes diarrhoea. 

Bismuth subsalicylate may cause side effects like ringing or buzzing in the ears. If you get such symptoms, consult your doctor. 

Take prescription medications 

If the over-the-counter drugs don’t work, consult your doctor immediately. Take your prescribed medication on time and never skip your doses. If your symptoms do not set in, consult your doctor. 

Prevention of Food Poisoning 

 Certain small habits can prevent food poisoning. 


Wash your hands properly before cooking. Keep your cooking area also clean to avoid any contamination. Microorganisms can survive up to 50℃.  

So, clean the kitchen area with proper disinfectant and keep the kitchen away from pests and cockroaches. Wash your vessels properly and dry them in adequate sunlight. 


Keep raw foods like chicken and fish away from cooked and ready-to-eat foods. Utensils, cutting boards and knives should be kept separate for raw foods.  

Make sure to clean the knives, utensils and cutting board properly after cooking, as the microorganism can stay alive for an extended period. 


Cook the foods to their right temperature. At the same time, do not overcook the foods as the nutrients will be lost. 

Ensure you properly cook the animal foods to kill all the live pathogens. Cover the cooked food to avoid flies or other pests contaminating the cooked food. 


Refrigerate the cooked leftover foods properly. When you consume the refrigerated food, make sure you reheat them at the correct temperature and then consume them. 

Improper heating can aggravate the microorganism’s growth and further contaminate the food. 

When to see a doctor?

 Food poisoning usually cures on its own with a lot of rest and fluid intake. Yet, if you or someone you know is having severe symptoms of illness, you need to consult a doctor immediately.  

Consult your doctor if the symptoms do not settle within two days. And further, if you have symptoms that are listed below. 

  • Bloody diarrhoea,
  • High fever assisted with chills,
  • Frequent vomiting and diarrhoea,
  • Severe dehydration,
  • Headache,
  • Diarrhoea that prolongs for more than three days and
  • No urination or little urination, dry mouth and dizziness.


Hygienic habits can help avoid food poisoning. Wash your hands regularly, especially before eating. Drink only boiled water, and make sure you boil the water at the right temperature. 

Follow proper self-hygiene habits. Wash hands with water and soap after using the washroom. Food poisoning symptoms will set in after two days, and in most cases, it does not require hospitalisation. In rare cases, it can be life-threatening. 


What foods should I eat if I have food poisoning symptoms? 

When you have food poisoning, there is a possibility of getting dehydrated. Drink more water and electrolytes to avoid dehydration. Consume light foods and avoid any spicy and oily foods. If your symptoms do not settle, consult your doctor immediately. 

How can food poisoning be prevented? 

Certain habits can prevent food poisoning. Wash your hands properly before eating. And keep your cooking area clean and free from any pests. Ensure you cover the cooked food properly to avoid any flies contaminating the food. 

How long do most cases of food poisoning typically last? 

The symptoms of food poisoning depend on the type of pathogen that has caused the infection. Usually, the symptoms last for about 4–7 days. 

Which foods are commonly associated with food poisoning? 

Animal foods like chicken, red meat and mutton. Raw milk and egg. The products that are made from raw milk like milkshakes. Undercooked seafood, sprouts and raw flour.

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