Introduction 

Food poisoning is an illness caused by eating contaminated food. Most people get better without the need for treatment.

In most cases, food that causes food poisoning is contaminated by bacteria, such as salmonella or Escherichia coli (E. coli), or a virus, such as the norovirus.

The symptoms of food poisoning usually begin 1-3 days after eating contaminated food. They include:

  • feeling sick
  • vomiting
  • diarrhoea 
  • stomach cramps

Some toxins can cause food poisoning within a much shorter time. In these cases, vomiting is the main symptom.

Foods particularly susceptible to contamination if not handled, stored or cooked properly include:

  • raw meat and poultry
  • raw eggs
  • raw shellfish
  • unpasteurised milk
  • 'ready to eat' foods, such as cooked sliced meats, pâté, soft cheeses and pre-packed sandwiches

How is food contaminated?

Food can become contaminated at any stage during production, processing or cooking. For example, food poisoning can be caused by:

  • not cooking food thoroughly (particularly poultry, pork, burgers, sausages and kebabs)
  • not storing food that needs to be chilled at below 5°C correctly
  • leaving cooked food for too long at warm temperatures  
  • someone who is ill or who has dirty hands touching the food
  • eating food that has passed its ‘use by’ date
  • cross-contamination (the spread of bacteria, such as E. coli, from contaminated foods)

Read more about the causes of food poisoning.

Treating food poisoning

Most people with food poisoning get better without the need for treatment. 

To help relieve your symptoms you should rest and drink plenty of fluids. It is best to avoid food until you feel much better. When you start eating again, choose foods that are easily digested, such as toast.

It's important that you do not become dehydrated because it will make you feel worse and lengthen your recovery.

Try to drink as much water as you can, even if you can only sip it, particularly every time you pass diarrhoea.

Oral rehydration salts (ORSs) are recommended for people vulnerable to the effects of dehydration, such as the elderly and those with another health condition (see below).

ORSs help replace salt, glucose and other important minerals lost through dehydration. They are available in sachets from pharmacies and you dissolve them in water to drink.

Read more about treating food poisoning.

When to see your GP

It's not usually necessary to see your GP if you have food poisoning. You only need to see them if:

  • your symptoms are severe and do not improve after a few days
  • you have a high temperature (fever) of 38°C (100.4°F) or over 
  • you have symptoms of severe dehydration, such as sunken eyes and passing small quantities of dark, strong smelling urine
  • there has been an outbreak of similar cases of food poisoning linked to a possible source of contamination
  • you have a baby with food poisoning

Occasionally, food poisoning can have more serious effects on a person’s health, particularly if they are vulnerable to infection. For example, if you are over 65 years of age, or you have a condition that weakens your immune system, such as HIV or cancer, your risk of developing more serious symptoms is increased. Babies are also at increased risk.

Signs that you may have a more serious case of food poisoning that requires medical attention include:

  • vomiting that lasts for more than two days
  • not being able to keep liquids down for more than a day
  • diarrhoea that lasts for more than three days or is bloody
  • fever 

Read more about when to seek medical advice for food poisoning.

Who is affected?

It's difficult to know exactly how many people get food poisoning because mild cases often go unreported.

However, the Food Standards Agency estimates that food poisoning affects up to 5.5 million people in the UK each year.

Page last reviewed: 27/03/2013

Next review due: 27/03/2015