Food poisoning or gastroenteritis?

Food poisoning and gastroenteritis are two types of illness whose symptoms are very similar to each other. This means that it can be difficult to determine which of these illnesses you have.

Food poisoning

Food poisoning develops as a result of eating or drinking something which is contaminated, usually by bacteria, although this can include toxins and parasites. Symptoms such as nausea, vomiting and diarrhoea often occur within 48 hours of this consumption.


Gastroenteritis or ‘stomach flu’ is caused by a viral infection which accounts for the majority of cases. Other cases are caused by bacterial infection and parasites. This can also be caused by contaminated food and water.

Gastroenteritis causes an inflammation of the digestive tract, specifically the stomach and intestines. If the stomach is affected, the illness is known as ‘gastritis’: similarly if the intestines are infected it is known as ‘enteritis’.

If both the stomach and intestines are infected then it is known as gastro-enteritis.

Symptoms of gastroenteritis are very similar to those of food poisoning –which may account for the confusion –and include fever, nausea, stomach bloating and diarrhoea.

What needs to be borne in mind is that gastroenteritis is not caused by a flu virus. It is often referred to as ‘stomach or gastric flu’but it is caused by either a viral or bacteria infection or NOT the influenza virus.

It may be easier to think of gastroenteritis as a ‘stomach bug’.

What is the difference between these two?

It is argued that the main difference is that food poisoning is an illness caused by infected (contaminated) food whereas gastroenteritis is caused by a viral/bacterial infection.

But because the symptoms of these illnesses are similar, many people assume that they have food poisoning when it fact that have gastroenteritis.

This is entirely understandable.

Here is a short description of each which may help to clarify matters:

Aspects of food poisoning

  • Caused by contaminated food and/or water
  • Spread by the consumption of any infected food product
  • Causes abdominal pain, nausea, vomiting and diarrhoea
  • Can lead to dehydration, kidney failure and reactive arthritis in severe cases.

Food poisoning occurs when a food product is consumed which is contaminated by bacteria. These bacteria attach themselves to the lining of the intestines and start to multiply. Toxins are then released which attack cells within this lining that results in the symptoms described above.

These toxins can be absorbed by the body which may cause problems elsewhere.

So, food poisoning occurs due to the bacteria in the contaminated food and the toxins produced.

Aspects of gastroenteritis

  • Caused by an infection (viral or bacterial)
  • Spread by personal contact although it can be transmitted through food or water.
  • Causes fever, bloated abdomen, watery diarrhoea, aches and pains and vomiting.
  • May lead to dehydration in serious cases

Gastroenteritis develops when a virus or bacteria, such as norovirus, enters the digestive system. Once there it negatively interacts with organs such as the intestines, causing side effects such as diarrhoea.

This virus or bacteria can react with food which passes through the digestive tract which results in an infection.

A further reaction is where toxins are released into the digestive tract which can cause damage to the internal organs. One sign of this is an inflammation of the stomach or gastritis.

So, gastroenteritis occurs as a result of a viral or bacteria infection within the digestive system (stomach and intestines).

We hope that this helps to clear up any confusion between these two similar illnesses. But contact your GP if you are unsure.

Food Poisoning Guide

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