Food poisoning occurs when food or water contaminated with harmful germs (microbes), poisons (toxins) or chemicals is eaten or drunk. It usually causes diarrhoea, with or without being sick (vomiting). However, other problems can be caused by eating contaminated food. In most cases, symptoms clear away over several days but sometimes it takes longer. The main risk is lack of fluid in the body (dehydration), which can develop more quickly and be more severe in children. The main treatment is to give your child lots to drink to try to avoid dehydration. Any suspected case of food poisoning from eating takeaway or restaurant food should be reported to your local Environmental Health Office. It is important to follow the '4 Cs' to help prevent food poisoning (see below).
What is food poisoning?
Food poisoning occurs when food or water contaminated with harmful germs (microbes), poisons (toxins) or chemicals is eaten or drunk. When we think of food poisoning, we usually think of the typical gastroenteritis - an infection of the gut (intestines) - which usually causes diarrhoea with or without being sick (vomiting). However, sometimes other symptoms or problems, such as feeling sick (nausea) and tummy (abdominal) cramping pain, can arise from eating contaminated food. Food poisoning can be caused by:
Campylobacter are the most common germs (bacteria) that cause food poisoning in the UK. Other bacteria that can cause food poisoning include:
- Escherichia coli (usually shortened to E. coli).
- Clostridium perfringens.
These are another type of microbe. Parasites are living things (organisms) that live within, or on, another organism. Examples include cryptosporidium, Entamoeba histolytica and giardia parasites. Food poisoning caused by parasites is more common in the developing world.
In the UK, the most common parasite that can cause food poisoning is toxoplasma. This is a parasite that lives in the gut of a number of animals, including cats. Food poisoning can occur if food or water is contaminated with the stools (faeces) of infected cats. It can also occur if raw or undercooked meat from another animal carrying the parasite is eaten. The infection is known as toxoplasmosis. Symptoms of this type of food poisoning include swollen lymph glands and sometimes a skin rash.
Toxins and chemicals
Toxins produced by bacteria can also contaminate food, as well as the bacteria themselves. For example, the bacterium Staphylococcus aureus can contaminate ice cream and its toxins can lead to food poisoning. The bacterium Bacillus cereus can contaminate rice. If contaminated rice is reheated and eaten, the toxins produced can lead to food poisoning.
Note: this is a general leaflet about food poisoning. There are separate leaflets that give more details about some of the different microbes that cause food poisoning.
How does food become contaminated?
Contamination of food can occur because of problems in food production, storage or cooking. For example:
- Not storing food correctly or at the correct temperature - for example, not refrigerating food. This is particularly a problem for meat and dairy products.
- Inadequate cooking of food (undercooking or not cooking hot enough). Germs (bacteria) are often found in raw meat, including poultry. Adequate cooking usually kills the bacteria.
- Contamination by someone preparing the food who has not followed food hygiene rules and has not washed their hands properly.
- Contamination from other foods (cross-contamination). For example, not washing a board used to prepare raw meat before you cut a slice of bread using the same board. Storing raw meat in the fridge above food that is ready-to-eat and so allowing raw meat juices to drip on to the food below.
- Bacteria can also be present in unpasteurised milk and cheese. The pasteurisation process kills the bacteria.
How does water become contaminated?
Water can become contaminated with bacteria or other germs (microbes) usually because human or animal stools (faeces) get into the water supply. This is particularly a problem in countries with poor sanitation. In such countries, food may also be washed and prepared using contaminated water. So, for example, in countries with poor sanitation, your child should always avoid:
- Drinking tap water.
- Having ice cubes in drinks (as the ice may have been made from tap water).
- Brushing teeth with tap water.
- Eating salads (as the lettuce, tomatoes, etc, may have been washed in contaminated water).
- Eating uncooked vegetables (as they may have been washed in contaminated water).
How common is food poisoning?
Food poisoning is very common. The Food Standards Agency (FSA) previously reported only the most serious cases but their figures now include mild cases as well. Their most recent statistics report that there are more than 500,000 cases of food poisoning in the UK every year from known causes. If unidentified causes were included as well, this figure would be more than doubled.
How long does it take for food poisoning to develop?
For most cases of food poisoning, symptoms tend to come on within one to three days of eating the contaminated food. However, for some types of food poisoning, this incubation period can be as long as 90 days.
What are the usual symptoms of food poisoning?
- The main symptom is diarrhoea, often with being sick (vomiting) as well. Diarrhoea is defined as 'loose or watery stools (faeces), usually at least three times in 24 hours'. Blood or mucus can appear in the stools with some infections.
- Crampy pains in your child's tummy (abdomen) are common. Pains may ease for a while each time some diarrhoea is passed.
- A high temperature (fever), headache and aching limbs sometimes occur.
If vomiting occurs, it often lasts only a day or so but sometimes longer. Diarrhoea often continues after the vomiting stops and commonly lasts for several days or more. Slightly loose stools may persist for a week or so further before a normal pattern returns. Sometimes the symptoms last longer.
Symptoms of lack of fluid in the body (dehydration)
Diarrhoea and vomiting may cause dehydration. If you suspect your child may be becoming dehydrated then you should seek medical advice urgently. Children, especially young children, infants and babies, can become severely dehydrated and very ill very quickly. Mild dehydration is common and is usually easily reversed by drinking lots of fluids.
Symptoms of dehydration in children include:
- Passing little urine.
- A dry mouth.
- A dry tongue and lips.
- Fewer tears when crying.
- Sunken eyes.
- Being irritable.
- Having a lack of energy (being lethargic).
Symptoms of severe dehydration in children include:
- Pale or mottled skin.
- Cold hands or feet.
- Very few wet nappies.
- Fast (but often shallow) breathing.
Severe dehydration is a medical emergency and immediate medical attention is needed.
Dehydration is more likely to occur in:
- Babies under the age of 1 year (and particularly those under 6 months old). This is because babies don't need to lose much fluid to lose a significant proportion of their total body fluid.
- Babies under the age of 1 year who were a low birth weight and who have not caught up with their weight.
- A breast-fed baby who has stopped breast-feeding during their illness.
- Any baby or child who does not drink much when they have a gut infection (gastroenteritis).
- Any baby or child with severe diarrhoea and vomiting. (For example if they have passed five or more diarrhoeal stools and/or vomited two or more times in the previous 24 hours).
How is food poisoning diagnosed and are tests required?
Most people will recognise food poisoning from their typical symptoms. If symptoms are mild, you do not usually need to seek medical advice or give your child any specific medical treatment apart from making sure they have lots to drink.
However, it is very important to seek urgent medical advice if your child is unwell, especially if they are becoming lacking in fluid in the body (dehydrated). The doctor may ask you questions about recent travel abroad or any ways that your child may have eaten or drunk contaminated food or water. The doctor will also usually check your child for signs of dehydration.
Your doctor may ask for a stool (faeces) sample to be collected and sent to a laboratory. This can then be examined in the laboratory to look for the cause of the infection. A stool sample is not always needed. Your doctor is likely to suggest one in certain situations, such as:
- If your child has recently been abroad.
- If your child is very unwell.
- If your child has blood or pus in their stools.
- If your child's diarrhoea is not settling after a week.
- If your child has recently been in hospital or had antibiotic treatment.
- If your child has another medical condition, particularly one which affects their immune system.
- If the doctor is not sure that your child has food poisoning or a gut infection (gastroenteritis)
The reason a stool sample is not always needed is that in many cases knowing what germ your child has does not make any difference to the treatment they need. Most cases of food poisoning get better on their own even before the stool test result is back.
If your child is very unwell, they may need admission to hospital. If this is the case, further investigations may be needed such as blood tests, scans or a lumbar puncture. This is to look for spread of the infection to other parts of the body.
When should I seek medical advice?
Most children who have gut infection (gastroenteritis) due to food poisoning have mild symptoms which will get better in a few days. The important thing is to ensure that they have plenty to drink. In many cases, you do not need to seek medical advice.
However, you should seek medical advice in the following situations:
- If your child is under the age of 6 months.
- If your child has an underlying medical condition (for example, heart or kidney problems, diabetes, history of premature birth).
- If your child has a high temperature (fever).
- If you suspect a lack of fluid in the body (dehydration) is developing (see earlier).
- If your child appears drowsy or confused.
- If your child is being sick (vomiting) and is unable to keep fluids down.
- If there is blood in their diarrhoea or vomit.
- If your child has severe tummy (abdominal) pain.
- Infections caught abroad.
- If your child has severe symptoms, or if you feel that their condition is becoming worse.
- If your child's symptoms are not settling (for example, vomiting for more than 1-2 days, or diarrhoea that does not start to settle after 3-4 days).
- If there are any other symptoms that you are concerned about.
What is the treatment for food poisoning?
Symptoms of gut infection (gastroenteritis) often settle within a few days or so as a child's immune system is usually able to clear the infection. Children can usually be treated at home. Occasionally, admission to hospital is needed if symptoms are severe or if complications develop.
Fluids to prevent lack of fluid in the body (dehydration)
You should encourage your child to take plenty of fluids. The aim is to prevent dehydration. The fluid lost in their sick (vomit) and/or diarrhoea needs to be replaced. Your child should continue with their normal diet and usual drinks. In addition, they should also be encouraged to drink extra fluids. However, avoid fizzy drinks or large amounts of concentrated fruit juices as these can make diarrhoea worse.
Babies under 6 months old are at increased risk of dehydration. You should seek medical advice if they develop gastroenteritis. Breast-feeds or bottle-feeds should be encouraged as normal. You may find that your baby's demand for feeds increases. You may also be advised to give extra fluids (either water or rehydration drinks) in between feeds.
Rehydration drinks may be advised for children at increased risk of dehydration (see above for whom this may be). They are made from sachets available from pharmacies and on prescription. You should be given instructions about how much to give. Rehydration drinks provide a perfect balance of water, salts and sugar. The small amount of sugar and salt helps the water to be taken up (absorbed) better from the gut (intestines) into the body. If rehydration drinks are not available for whatever reason, make sure you keep giving your child water, diluted fruit juice or some other suitable liquid. If you are breast-feeding, you should continue with this during this time. It is important that your child is rehydrated before they have any solid food.
If your child vomits, wait 5-10 minutes and then start giving drinks again but more slowly (for example, a spoonful every 2-3 minutes). Use of a syringe can help in younger children who may not be able to take sips.
Note: if you suspect that your child is dehydrated or is becoming dehydrated, you should seek medical advice urgently.
Fluids to treat dehydration
If your child is mildly dehydrated, this may be treated by giving them rehydration drinks. Read the instructions carefully for advice about how to make up the drinks and about how much to give. The amount can depend on the age and the weight of your child. If you are breast-feeding, you should continue with this during this time. It is important that your child is rehydrated before they have any solid food.
Sometimes a child may need to be admitted to hospital for treatment if they are dehydrated. Treatment in hospital usually involves giving rehydration solution through a special tube called a nasogastric tube. This tube passes through your child's nose, down their throat and directly into their stomach. An alternative treatment is with fluids given directly into a vein (intravenous fluids).
Eat as normally as possible once any dehydration has been treated
Correcting any dehydration is the first priority. However, if your child is not dehydrated (most cases), or once any dehydration has been corrected, encourage your child to have their normal diet. Do not 'starve' a child with gastroenteritis. This used to be advised but is now known to be wrong. So:
- Breast-fed babies should continue to be breast-fed if they will take it. This will usually be in addition to extra rehydration drinks (described above).
- Bottle-fed babies should be fed with their normal full-strength feeds if they will take them. Again, this will usually be in addition to extra rehydration drinks (described above).
- Older children - offer them some food every now and then. However, if he or she does not want to eat, that is fine. Drinks are the most important and food can wait until their appetite returns.
Medication is not usually needed
You should not give medicines to stop diarrhoea to children under 12 years old. They sound attractive remedies but are unsafe to give to children, due to possible serious complications. However, you can give paracetamol or ibuprofen to ease a high temperature (fever) or headache.
If symptoms are severe or persist for several days or more, a doctor may ask for a sample of the diarrhoea. This is sent to the laboratory to look for infecting germs (bacteria, parasites, etc). Sometimes an antibiotic medication or other treatments are needed, depending on the cause of the infection. An antibiotic may be needed, for example, if:
- Your child is less than 6 months old and has confirmed salmonella infection.
- Your child has blood in their diarrhoea.
- Your child has a condition where their immune system is not working as well as normal - for example, due to chemotherapy or an illness such as AIDS.
- Your child has recently been abroad. Certain infections usually acquired abroad, if confirmed, are usually treated with antibiotics. For example, giardia, cholera or amoebic infection.
Probiotics are generally not recommended for children with gastroenteritis or food poisoning from any cause. This may change if further research shows that they are helpful.
Antisecretory medicines are a newer group of treatments. They are designed to be used with rehydration treatment. They reduce the amount of water that is released into the gut during an episode of diarrhoea. They can be used for children who are older than 3 months of age. Racecadotril is the only antisecretory medicine available in the UK at the moment and is only available on prescription. It is not available in Scotland on prescription as it is felt there is not enough evidence yet about how effective it is.
Preventing the spread of food poisoning to others
Some infections causing diarrhoea and sickness (vomiting) are very easily passed on from person to person. The following are also recommended to prevent the spread of infection to others:
- Wash hands thoroughly after going to the toilet. Ideally, use liquid soap in warm running water but any soap is better than none. Dry properly after washing.
- Don't share towels and flannels.
- Regularly clean the toilets that are used. Wipe the flush handle, toilet seat, bathroom taps, surfaces and door handles with hot water and detergent at least once a day. Keep a cloth just for cleaning the toilet (or use a disposable one each time).
- Stay off school until at least 48 hours after the last episode of diarrhoea or vomiting.
If the cause of food poisoning is known to be (or suspected to be) a germ called cryptosporidium, your child should not swim in swimming pools for two weeks after the last episode of diarrhoea.
Are there any complications that can occur from food poisoning?
Complications are uncommon in the UK but are more common in young children or children with long-term illness. Possible complications include the following:
- Salt (electrolyte) imbalance and lack of fluid in the body (dehydration). This is the most common complication. It occurs if the salts and water that are lost in your child's stools (faeces) or sick (vomit) are not replaced by them drinking enough fluids. If your child can drink plenty of fluids then dehydration is unlikely to occur, or is only likely to be mild and will soon recover. Severe dehydration needs admission to hospital so that a 'drip' can be used to give fluid directly into a vein.
- Reactive complications. Rarely, other parts of your body can 'react' to an infection that occurs in your gut (intestines). This can cause symptoms such as joint inflammation (arthritis), skin inflammation and eye inflammation (either conjunctivitis or uveitis).
- Spread of infection to other parts of your child's body such as bones, joints or the meninges that surround their brain and spinal cord. This is rare. If it does occur, it is more likely if diarrhoea is caused by salmonella infection.
- Persistent diarrhoeal syndromes may rarely develop:
- Irritable bowel syndrome is sometimes triggered by a bout of food poisoning.
- Lactose intolerance can sometimes occur for a period of time after food poisoning. This is known as 'secondary' or 'acquired' lactose intolerance. Your child's gut (intestinal) lining can be damaged by the episode of gut infection. This leads to lack of a chemical (an enzyme) called lactase which is needed to help digest a sugar called lactose that is in milk. Lactose intolerance leads to bloating, tummy (abdominal) pain, wind and watery stools after drinking milk. The condition gets better when the infection is over and the gut lining heals. It is more common in children than in adults.
- Haemolytic uraemic syndrome is rare and is usually associated with food poisoning caused by a certain type of E. coli infection (E. coli O157). It is a serious condition where there is anaemia, a low platelet count in the blood and kidney failure. It is more common in children than in adults. If it is recognised and treated early then most children recover well.
- Malnutrition may follow some gut infections. This is very unlikely with food poisoning and is a much greater risk for children in developing countries.
- Reduced effectiveness of some medicines. During an episode of food poisoning, certain medicines that your child may be taking for other conditions, such as epilepsy, may not be as effective. This is because the diarrhoea and/or vomiting means that reduced amounts of the medicines are taken up (absorbed) into your child's body.
Reporting the food poisoning episode
Any suspected case of food poisoning from eating takeaway or restaurant food should be reported to the local Environmental Health Office. This is so that the business can be investigated by environmental health officers. Further actions may be taken if there is a problem with their food hygiene practices. It is hoped that this will help to reduce the chance that other people will get food poisoning. You can find your local food standards enforcer from the Food Standards Agency Report a Food Problem. If your doctor suspects or confirms that your child has food poisoning, they are also required by law to report this.
Can food poisoning be prevented?
The Foods Standards Agency in the UK has identified the '4 Cs' to help prevent food poisoning:
- Keep work surfaces and utensils clean.
- Wash and dry hands regularly but especially after going to the toilet, before preparing food, after handling raw food and before touching ready-to-eat food.
- Don't prepare food for others if you have diarrhoea or sickness (vomiting).
- Cover any sores or cuts on hands with a waterproof plaster before you touch food.
- Change dishcloths and tea towels regularly.
- Make sure that you cook food thoroughly, especially meat. This will kill germs (bacteria). Food should be cooked right through and be piping hot in the middle.
- If you are reheating food, it too needs to be cooked right through and be piping hot in the middle.
- Don't reheat food more than once.
- Food that needs to be chilled or refrigerated should be. If food is left out of the fridge, bacteria may multiply to levels that can cause food poisoning.
- Your fridge needs to be kept between 0°C and 5°C. Also, don't leave the door open unnecessarily.
- Cool leftover food quickly and then refrigerate. Taking it out of the cooking pot and putting it into a shallow container can speed the cooling process up.
This occurs when bacteria pass from foods (commonly, raw foods) to other foods. It can occur if:
- Foods touch directly.
- One food drips on to another.
- Your hands or utensils or equipment such as knives or chopping boards touch one food and then another.
It is important to:
- Wash your hands after touching raw foods.
- Separate raw and cooked or ready-to-eat foods.
- Keep raw meat in a sealable container at the bottom of the fridge.
- Avoid using the same surface or chopping board for preparing raw and ready-to-eat foods.
- Make sure that knives and utensils are cleaned after preparing raw foods.
Special precautions may also be needed to prevent food poisoning if you are travelling abroad. See separate leaflet called Traveller's Diarrhoea for more details. For example, avoid water and other drinks that may not be safe and avoid food washed in unsafe water.
Further help & information
Dr Colin Tidy
Dr Mary Harding
Dr Laurence Knott