Most of us at one point or another will have the misfortune to suffer from food poisoning – a bout of sickness caused by eating contaminated food.

Every year millions of people will undergo bouts of nausea and vomiting thanks to something they ate. Fortunately, it's not usually serious and most people get better within a few days without treatment.

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Find out more here about what causes food poisoning, what the symptoms are – and how long you can expect to be ill should you suffer from it.

Why do we get food poisoning?

In most cases, food poisoning comes from eating food contaminated by bacteria, such as campylobacter, salmonella or Escherichia coli (E. coli), or a virus.

Food can be contaminated in a number of ways – by not being cooked thoroughly (especially in the case of meat), by being left for too long after cooking and before eating, by not being reheated properly after previous cooking, or by not being stored at the right temperature.  It could also have been handled by someone ill or with dirty hands.

What are the symptoms of food poisoning?

The symptoms of food poisoning usually begin within one to two days after eating contaminated food, although they may start at any point between a few hours and several weeks later. 

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Symptoms are likely to include nausea, vomiting, stomach cramps, weakness and a loss of energy, loss of appetite, a high temperature or fever and chills, and in some cases diarrhoea.

How long will the symptoms of food poisoning last?

In the UK, campylobacter bacteria are the most common cause of food poisoning. The bacteria are usually found on raw or undercooked meat (particularly poultry), unpasteurised milk and untreated water.

The incubation period (the time between eating contaminated food and the start of symptoms) for food poisoning caused by campylobacter is usually between two and five days. The symptoms usually last less than a week.

Salmonella bacteria are often found in raw or undercooked meat, raw eggs, milk, and other dairy products.  Its incubation period is usually between 12 and 72 hours. The symptoms usually last around four to seven days.

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Listeria bacteria may be found in chilled, ready-to-eat foods, including pre-packed sandwiches, cooked sliced meats and soft cheeses. All of these foods should be eaten by their ‘use by’ dates.

The incubation period can vary considerably, from a few days to several weeks. The symptoms will usually pass within three days. It can affect pregnancy, so should you come down with food poisoning after eating chilled food while pregnant, seek medical help.

E. coli bacteria are found in the digestive systems of many animals, including humans. Most cases of E. coli food poisoning occur after eating undercooked beef (particularly mince, burgers and meatballs) or drinking unpasteurised milk.

The incubation period for E. coli food poisoning is typically one to eight days. The symptoms usually last for a few days, up to two weeks.

Another bacteria that causes food poisoning, Clostridium perfringens, usually comes from eating contaminated meat and poultry. Its incubation period is between 8 to 22 hours and it will give sufferers diarrhoea and stomach cramps that last for around 12 hours.

How is food poisoning treated?

Most people with food poisoning don't need any specific treatment. Until you feel better, rest and drink plenty of fluids to prevent dehydration.  When you’re ready to eat have small, light meals at first and stick to bland foods until you begin to feel better.

You should contact your GP if your symptoms are severe – for example, if you're unable to keep down any fluids at all; if your symptoms don't start to improve after a few days; or you have symptoms of severe dehydration – these include confusion, a rapid heartbeat, and passing little or no urine.

It’s also worth seeing a doctor about food poisoning if you're pregnant, over 60, have a long-term underlying condition such as heart disease, diabetes or kidney disease, or if you suspect your baby or young child has food poisoning.