Food Poisoning - Introduction, Symptoms & Food Preservation

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Food poisoning is not a serious disease or illness until it is treated on time. Food poisoning takes place when the individual eats contaminated food and in many cases, the food is adulterated by bacteria or viruses or parasite but in most common cases, the food is contaminated by bacteria. The causative bacteria of food poisoning include Listeria, Salmonella, and E.Coli. The viruses that can affect the food causing food poisoning include Norovirus. This can be serious if not treated on time. Other viruses include rotavirus, astrovirus. The symptoms of food poisoning caused by all viruses will be the same but the food poisoning caused by rotavirus and astrovirus when compared to Norovirus is less common. The food poisoning caused due to parasites is still rarer when compared to the bacteria but they may cause severe symptoms on entering the digestive tract of the individual. The most common parasite seen in the case of parasitic food poisoning is Toxoplasma. This parasite is generally found in animal litter boxes especially cats. The symptoms due to parasitic infection present late since, the parasite can survive in the human digestive system for years without getting detected. But in people with lower immunity, the symptoms can be presented soon and they can turn out to be fatal at times.

Food Poisoning Causes and Symptoms 

There are several reasons the food that we eat might get contaminated and as a result, causes food poisoning. They are:

  • If the food that we prepare is not cooked properly or undercooked, since any pathogens on the surface of the raw materials get killed if it is thoroughly cooked.

  • Any fruits, if consumed without washing, has also a vide chance of causing food poisoning.

  • Eating any stale food

  • Eating food that is not stored properly at proper temperatures.

  • Eating fruits and bread that are stale and expired and are covered with fungus.

  • Any person already inflicted with any bacterial or viral infection if shares food with a healthy individual might also have a chance that infection is spread through the food. 

  • The foods that can be easily contaminated are raw meat, eggs, and milk that is not pasteurized and stored at higher temperatures


There are different types of bacteria found on various food products that are responsible for food poisoning. The bacteria Salmonella is found on raw meat and poultry and even unfiltered water. Infection caused due to this bacteria has an incubation period( from the day the bacteria is ingested to the day the symptoms start to appear) of a minimum of 3-6 days.

The ready to eat items that are served have a higher chance of being affected with the bacteria called Listeria. These ready to eat items have an expiry date mentioned and storage instructions on it and they need to be consumed accordingly. The incubation period varies between 5 days to several weeks. This particular bacteria is very dangerous among pregnant women and has known to cause even a miscarriage. 

One of the common bacteria is the E.coli which is usually found in the digestive system of human beings and animals. While few varieties are very helpful in carrying out the digestive function properly, there are some varieties that are equally hazardous. The incubation period varies between 7-10 days.

Campylobacter is a kind of bacteria generally found on raw meat and dairy items. The incubation period of this varies between 3-5 days. The most common type of food poisoning is caused due to this bacteria.


Though there are several reasons for the virus being a cause for food poisoning the most common source is the seafood that includes oysters and shellfish. The incubation period varies between 12 hours to 48 hours.


The parasitic infection though is not common but the symptoms will be very fatal. Few infections due to parasite are:

  • Amoebiasis is a dysentery due to entamoeba histolytica.

  • Cryptosporidium is a parasite that causes cryptosporidiosis.


The symptoms of food poisoning include:

  • Headache

  • Abdominal pain

  • Vomiting

  • Loose stools

  • A rise in body temperature

  • Dryness in the mouth and feeling of tastelessness

  • Severe infections might also show symptoms like increased breathing, dehydration, and bloody stools.

  • If the infection is in small intestines then generally the symptoms presented are watery diarrhea, fever with chills, vomiting, and weakness.

  • If the infection is in large intestines then diarrhea would be more like mucousy and bloody associated with vomiting and pain abdomen. The chances of infection spreading to the bloodstream are more causing the symptoms to be life-threatening. 

Food Poisoning Diagnosis and Treatment 

The diagnosis of food poisoning is often based on the duration of the illness and the presenting symptoms. Apart from general history taking like whether any outside food is consumed in recent days, a physical examination is also conducted by the medical practitioner to differentiate between food poisoning and other ailments. For example, abdominal pain is a common symptom in food poisoning and certain other ailments like appendicitis, bladder infections, kidney stones, and uterine problems, etc. A proper abdominal examination helps the doctor evaluate the probable reason for the pain. Food poisoning is often associated with a rise in body temperature, diarrhea and also vomiting in extreme cases. The diagnosis also includes laboratory investigations like blood examination, stool culture to know whether there is a presence of any bacteria or other parasites to rule out which pathogen is responsible for food poisoning.  


The first line of treatment includes the replacement of the lost body fluids by intravenous injections that include electrolytes like sodium, potassium, etc so that the body fluid is maintained properly. Mild cases of food poisoning can be managed by giving oral rehydration solutions whereas if the dehydration levels are more then such patients need hospitalization for further management of illness. 

To stop further spread of the infection that leads to dehydration, antibiotics are administered. Food poisoning is carefully managed during pregnancy so that the infection does not affect the growing fetus.

Along with medicines, even diet is prescribed such that it does not cause any irritation to the stomach and intestinal lining. Especially caffeinated drinks are said to irritate the digestive tract. Most of the time a bland diet is advised to overcome disturbed metabolism due to vomiting and diarrhea. Furthermore, plenty of rest is recommended to overcome the weakness. 

Diet Management

After the episode of food poisoning, the digestive tract will be very weak and the process of digestion of regular food will be difficult. Hence, a diet rich in nutrients which is easy to digest and soft on the stomach with fewer fats is advised that includes:

Bananas, oats, boiled potatoes, and green leafy vegetables which are properly cooked. Raw or undercooked food is avoided so that the infection does not relapse due to the presence of any pathogens on the food substances. Aerated drinks, spicy foods, food with high sugar content, and deep-fried foods are completely avoided. Milk and milk products also cause gastric disturbances and hence are recommended to be avoided. Smoking and alcohol consumption should also be avoided.

Difference Between Food Poisoning and Stomach Flu and Prevention 

Food poisoning and stomach flu are differentiated based on whether the infection is caused due to ingestion of contaminated food or through other means like getting in contact with the body secretions of the infected person. Though the symptoms presented appear to be the same but the duration of the illness varies. Viral gastroenteritis is a type of illness categorized under stomach flu by many physicians. The infection due to some less potent virus will develop late in an individual but they will ultimately resolve in 12-24 hours. The virus responsible for this is either adenovirus or rotavirus. The food poisoning, however, has symptoms that will last for long and also the symptoms will be fatal if not treated in time. In most cases, any bacterial infection in the digestive tract causing dehydration is considered under food poisoning.


Maintaining hygiene is the first step towards preventing any diseases caused due to pathogens. Following food safety measures is the best way to prevent food poisoning. Some of the measures that can be adopted to prevent food poisoning are:

  • Avoid eating street-side food.

  • Avoid eating raw or undercooked food.

  • Consuming dairy products within their expiry date.

  • Avoid eating meat and poultry that is not washed and cooked properly under hygienic conditions

  • Avoid eating fruits and vegetables that are not washed properly

  • Always use clean and hygienic utensils to prepare the food and to serve the food.

  • Store the food materials in proper temperatures and in hygienic conditions.

  • Never keep the cooked food open and always cover the food to avoid flies to sit on it.

  • The use of probiotics will decrease the chances of food poisoning by maintaining digestive health.

Chemical Causes of Food Poisoning 

Chemical food poisoning is caused when an individual ingests food substances like animals and plants that contain toxins that are present in them naturally. These chemicals include sulfur, serotonin, phenols, alkaloids, etc. Some variety of mushrooms and seafood are said to cause allergies and food poisoning due to their high level of toxin content in it. There are millions of natural and synthetic chemicals that are known to cause a variety of health issues in human beings. Chemicals are found in homes, playgrounds, workplaces. The early it diagnosed, the easier it is to be treated. 

There is a poisoning caused due to consuming fish stored in poor and unhygienic conditions and improper temperature. This poisoning is known as Scrombroid poisoning. The effects are almost immediate and can cause difficulty in breathing and swallowing within 2-3 hours of consumption. Few other varieties of fish can also cause neurological disturbances. Intake of a variety of mushroom called Amanita Phalloids causes complete liver and kidney failure and is considered one among the deadliest of the mushroom species that account for maximum fatalities. 

The Symptoms from these Chemical Poisonings Include:

  • Itching

  • Swelling of face and ankles

  • Breathing difficulties 

  • Difficulty in swallowing

  • Redness and rashes on the skin

FAQ (Frequently Asked Questions)

1. What is Botulism?

Ans: Botulism is caused by the bacteria clostridium botulinum. These bacteria are commonly found in soil and water. Foodborne Botulism is caused when an individual ingests food that contains these bacteria. The symptoms include droopy eyes, blurred vision, difficulty in speech, tiredness. If the illness progresses then fever and diarrhea are also noticed. Bacterial botulism occurs mostly in children when the bacteria starts developing in the intestines. This bacteria then release toxins that can even cause paralysis in children. The bacteria can produce toxins when it comes to contact with favorable temperatures and low oxygen levels. Botulism in adults is also referred to as adult intestinal toxemia. The disease can be prevented by boiling and heating food above 80-degree celsius. With this temperature, the toxin can be destroyed. However, the effect of temperature on organism varies.

2. What is Hemorrhagic E.coli?

Ans: Hemorrhagic E.coli causes inflammation of the intestines that lead to blood in the stools. In children, this can even further develop into HUS( hemolytic uremic syndrome ). Apart from consuming contaminated food, this can also spread by drinking contaminated water, from swimming pools and from schools and daycare centers. 

3. What is Stomach Flu?

Ans: Stomach flu is also called viral gastroenteritis. The infection spreads through food or by coming in contact with the secretions of the infected individual. The infection proves to be fatal in individuals who have a compromised immune system. The symptoms include diarrhea which is watery, stomach pain, nausea with vomiting. Since the infection is due to virus there is no known treatment for it. The illness needs to be properly managed by maintaining the hydration level of the patient and avoid exposure to food that is contaminated. In many mild conditions, the symptoms subside within 24 hours.

4. What are the Organisms that Commonly Cause Food Poisoning?

Ans: The organisms that cause maximum food poisoning include:

  • Campylobacter

  • Norovirus

  • Staphylococcus aureus

  • Clostridium perfringens

  • salmonella.