Food poisoning: symptoms, how long it lasts and what to do

The NHS lists the symptoms of food poisoning as feeling sick or being sick, diarrhoea, tummy pain, a high temperature and feeling generally unwell. NHS inform describes the main symptoms of gastroenteritis, which includes bacterial food poisoning, as sudden watery diarrhoea, feeling sick, vomiting (which can be projectile) and a mild fever, with some people also having loss of appetite, aching limbs and headaches.

The NHS says symptoms usually start within a few hours or a few days of eating the food that caused the infection. Sometimes they do not start for a few weeks, so the last meal you ate is not always the cause.

The NHS says food poisoning is rarely serious and usually gets better within a week. NHS inform gives the same pattern for gastroenteritis, saying symptoms typically last less than a week but can sometimes last longer.

The length depends on the germ. The NHS says norovirus usually gets better in about 2 days, and that you will usually start to feel better in 2 to 3 days. If diarrhoea lasts more than 7 days or vomiting lasts more than 2 days, the NHS says to call 111.

The NHS says diarrhoea and vomiting can usually be treated at home and the most important thing is to have lots of fluids to avoid dehydration. NHS inform says there is not always a specific treatment, so you let the illness run its course.

• Stay at home and get plenty of rest.

• Drink lots of fluids, such as water or squash, taking small sips if you feel sick.

• Eat when you feel able to; it may help to avoid foods that are fatty or spicy.

• Take paracetamol if you are in discomfort, checking the leaflet before giving it to a child.

• Do not have fruit juice or fizzy drinks, as they can make diarrhoea worse.

• Do not give children under 12 medicine to stop diarrhoea, and do not give aspirin to children under 16.

• Carry on breast or bottle feeding a baby, giving small feeds more often if they are being sick, and do not make formula weaker.

The NHS says to speak to a pharmacist if you or your child (over 5 years) have signs of dehydration such as dark, smelly pee or peeing less than usual, if you are an older person, have a weakened immune system or other conditions that increase your risk of dehydration, or if you need to stop diarrhoea for a few hours.

The pharmacist may recommend oral rehydration powder that you mix with water, or a medicine to stop diarrhoea for a few hours such as loperamide, which is not suitable for children under 12 according to the NHS.

Food poisoning itself comes from contaminated food, but many of the germs behind it also spread from person to person. NHS inform says the bugs that cause gastroenteritis can spread very easily, through small particles of vomit or poo from an infected person getting into your mouth, for example via close contact or touching contaminated surfaces. The NHS says norovirus spreads through poo and can spread to others very easily.

NHS inform says a person with gastroenteritis is most infectious from when their symptoms start until 48 hours after all their symptoms have passed, and may be infectious for a short time before and after.

• Stay off work until at least 48 hours after the symptoms have passed, and avoid visiting anyone in hospital during this time.

• Wash your hands frequently and thoroughly with soap and warm water, particularly after using the toilet and before preparing food. Do not rely on alcohol hand gels.

• Disinfect surfaces with a bleach-based household cleaner and wash contaminated clothing or bedding separately on a hot wash.

• Do not prepare food for other people when you are infected, if possible, and do not share towels, flannels, cutlery or utensils.

The NHS says food poisoning is caused by eating something that has been contaminated with germs. This can happen if food is not cooked or reheated thoroughly, is not stored correctly (for example it has not been frozen or chilled), is left out for too long, is handled by someone who is ill or has not washed their hands, or is eaten after its use-by date. Any type of food can cause food poisoning.

The NHS says the infections behind it are usually campylobacter bacteria (the most common cause in the UK), salmonella bacteria, E. coli bacteria and norovirus, the vomiting bug.

The NHS says to call 111 now if you are worried about a baby under 12 months, or if any of the following apply to you or your child:

• your child stops breast or bottle feeding while they are ill

• a child under 5 years has signs of dehydration, such as fewer wet nappies

• you or your child (aged 5 years or over) still have signs of dehydration after using oral rehydration sachets

• you keep being sick and cannot keep fluid down

• you have bloody diarrhoea or bleeding from the bottom

• you have diarrhoea for more than 7 days or vomiting for more than 2 days

The NHS says to call 999 or go to A&E if you or your child vomit blood or have vomit that looks like ground coffee, have green vomit (adults) or yellow-green or green vomit (children), may have swallowed something poisonous, have a stiff neck and pain when looking at bright lights, a sudden severe headache or a sudden severe tummy ache, blue, grey, pale or blotchy skin, lips or tongue, severe difficulty breathing or are confused or not responding as usual. Do not drive yourself to A&E.

NHS inform also lists people who should phone 111 or their GP urgently, including those with a fever over 38C, those with kidney disease, inflammatory bowel disease or a weak immune system who have diarrhoea and vomiting, and people who have returned from a part of the world with poor sanitation in the past few weeks.

Most people never need to see anyone. NHS inform says you do not normally need to see your GP, and that visiting a GP practice can put others at risk, so phone 111 or your GP if you are concerned. If your symptoms last, your GP may suggest sending a poo sample to a laboratory, and NHS inform says antibiotics may be prescribed if this shows a bacterial infection.

A private GP or urgent care appointment can be a way to be seen sooner, but the same advice applies: fluids, rest and watching for the warning signs above. If you work with food or in health or social care, follow your employer's guidance on when it is safe to return.