Signs and symptoms of food poisoning
In most cases of food poisoning, the food 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 within one to two days of eating contaminated food. Although the symptoms may begin at any point between a few hours and several weeks later.
The main symptoms include:
- feeling sick (nausea)
- diarrhoea, which may contain blood or mucus
- stomach cramps and abdominal (tummy) pain
- a lack of energy and weakness
- loss of appetite
- a high temperature (fever)
- aching muscles
In most cases, these symptoms will pass in a few days and you will make a full recovery.
What to do
Most people with food poisoning recover at home and don't need any specific treatment. However, there are some situations where you should see your GP for advice.
Until you feel better, you should rest and drink fluids to prevent dehydration. Try to drink plenty of water, even if you can only sip it.
You should eat when you feel up to it. Try small, light meals at first and stick to bland foods – such as toast, crackers, bananas and rice – until you begin to feel better.
Oral rehydration solutions, which are available from pharmacies, are recommended for more vulnerable people. This can include the elderly and those with another health condition.
Treating food poisoning
Food poisoning can usually be treated at home without seeking medical advice. Most people will feel better within a few days.
It's important to avoid dehydration by drinking plenty of water, even if you can only sip it. You will need to replace any fluids lost through vomiting and diarrhoea.
You should also:
- rest as much as possible
- eat when you feel up to it – sticking to small, light and non-fatty meals at first (bland foods such as toast, crackers, rice and bananas are good choices)
- avoid alcohol, caffeine, fizzy drinks and spicy and fatty foods because they may make you feel worse
Contact your GP if your symptoms are severe or don't begin to improve in a few days.
When to see your GP
While the symptoms can be alarming for parents/carers, it is important to note that diarrhoea usually lasts five to seven days. In most children it stops within two weeks. With vomiting, the usual duration is one or two days, and in most children it stops within three days.
Similarly for adults, vomiting for two days, and diarrhoea lasting for up to 10 days is not unusual.
You should contact your GP if:
- your symptoms are severe – for example, if you're unable to keep down any fluids because you are vomiting repeatedly (vomiting lasts more than two days for adults, 24 hours for children under two, or 12 hours for children one year or younger)
- your symptoms don't begin to improve after a few days - children with diarrhoea who have defecated (pooed) more than five times in the previous 24 hours, adults with diarrhoea lasting more than 10 days
- there is any blood in the diarrhoea
- you have symptoms of severe dehydration
- you're pregnant
- you're over 60
- your baby or young child has suspected food poisoning - usually other people who have eaten the same food will experience similar symptoms
- you have a long-term underlying condition, such as inflammatory bowel disease (IBD), heart valve disease, diabetes or kidney disease
- you have a weak immune system – for example, because of medication, cancer treatment or HIV
In these situations, your GP may send off a stool sample for analysis and may sometimes prescribe antibiotics, or they may refer you to hospital so you can be looked after more closely.
How is food contaminated?
Food can become contaminated at any stage during its production, processing or cooking.
For example, it can become contaminated by:
- not cooking food thoroughly (particularly meat)
- not correctly storing food that needs to be chilled at below 5C
- keeping cooked food unrefrigerated for a long period
- eating food that has been touched by someone who is ill or has been in contact with someone with diarrhoea and vomiting
- eating food that has passed its 'use by' date
- cross-contamination (where harmful bacteria are spread between food, surfaces and equipment)
Cross-contamination can occur, for example, if you prepare raw chicken on a chopping board and don't wash the board before preparing food that won't be cooked (such as salad)
This can lead to the harmful bacteria spreading from the chopping board to the salad.
It can also occur if raw meat is stored in a fridge above ready-to-eat meals and juices from the meat drip on to the food below.
Types of infection
Food contamination is usually caused by bacteria, but it can also sometimes be caused by viruses or parasites.
- Escherichia coli (E. coli)
Preventing food poisoning
The best way to avoid getting food poisoning is to ensure you maintain high standards of personal and food hygiene when storing, handling and preparing food.
The Food Standards Agency (FSA) recommends remembering the ’four Cs’:
- cross-contamination (avoiding it)
It's also recommended that you stick to a food’s ‘use by’ date and the storage instructions on the packet.
These steps are important because things such as a food's appearance and smell aren't a reliable way of telling if it's safe to eat.