Gastroenteritis from food poisoning is an
illness which is caused by eating contaminated food. Most people usually get better without the
need for any treatment. In the majority of cases, food which causes food poisoning is contaminated by bacteria, (e.g. salmonella or
Escherichia coli (E. coli)), or a virus (e.g. 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
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)
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.
It's not usually
necessary to see your doctor 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
Causes of food poisoning
Food can become contaminated at any
stage during its production, processing or cooking.
For example, you can
get food poisoning 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
- keeping cooked food
unrefrigerated for more than an hour
- eating food that has been
touched by someone who is ill with diarrhoea and vomiting
- cross-contamination (the
spread of bacteria, such as E. coli, from contaminated foods)
Cross-contamination
is a cause of food poisoning that is often overlooked. It occurs when harmful
bacteria are spread between food, surfaces and equipment.
For example, if you
prepare raw chicken on a chopping board and do not wash the board before
preparing food that won't be cooked (such as salad) harmful bacteria can be
spread from the chopping board to the food.
Cross-contamination
can also occur if raw meat is stored above ready-to-eat meals. If juices
from the meat drip on to the food below, it can contaminate it.
Food
contamination is usually caused by bacteria, but it can also
sometimes be caused by viruses or parasites. Some common sources of
contamination are described below.
In the UK,
campylobacter is the most common bacterial cause of food poisoning.
Campylobacter
bacteria are usually found on raw or undercooked meat (particularly
poultry), unpasteurised milk and untreated water. Undercooked chicken liver and
liver pâté are also common sources.
Salmonella bacteria
are often found in raw meat and poultry. They can also be passed into dairy
products such as eggs and unpasteurised milk.
Listeria bacteria may
be found in a range of chilled, ready-to-eat food, including:
- pre-packed sandwiches
- pâté
- butter
- soft cheeses, such as brie, camembert
or others with a similar rind
- soft blue cheese
- cooked sliced meats
- smoked salmon
With all of these
foods it is important they are eaten by their ‘use by’ dates.
Escherichia coli,
often known as E. coli, are bacteria found in the digestive systems of many
animals, including humans. Most strains are harmless but some strains can
cause serious illness.
Most cases of E. coli
food poisoning occur after eating undercooked beef (particularly mince, burgers
and meatballs) or drinking unpasteurised milk.
Raw shellfish,
particularly oysters can be a source of viral contamination. A study funded by
the Foods Standards Agency (FSA) found that three-quarters of oysters
sampled from harvesting beds within UK waters contained norovirus, although in
half of these it was only detected at low levels.
Currently, these
findings do not provide any greater indication of the risk of becoming ill at
the point where oysters are purchased and consumed.
The FSA advises that
older people, pregnant women, very young children and people who are unwell
should avoid eating raw or lightly cooked shellfish to reduce their risk of
getting food poisoning.
In the UK, food
poisoning from parasites is rare. It is much more common in the
developing world.
Toxoplasmosis is the
most likely cause of parasitical food poisoning in the UK. It is caused by
a parasite that is found in the digestive systems of many animals, particularly
cats.
Humans can get
toxoplasmosis by consuming undercooked contaminated meat or food or water
contaminated with the faeces of infected cats.
Symptoms of food poisoning
The symptoms of food poisoning usually
develop 1–3 days after eating contaminated food.
However, depending on
the type of food poisoning, symptoms can develop between one hour and
several weeks after eating contaminated food.
The most common
symptoms are:
- nausea
- vomiting
- diarrhoea
Other symptoms of
food poisoning include:
- stomach cramps
- abdominal pain
- loss of appetite
- a high temperature of 38°C
(100.4°F) or above
- muscle pain
- chills
Where food has been
contaminated by bacteria or chemicals, vomiting is the main symptom.
In these cases, vomiting can occur 15 minutes to six hours after
eating the food.
Most people make a
full recovery 12–48 hours after having food poisoning.
Most cases of food
poisoning do not require medical treatment. However, you should seek
medical advice if you have any of the following signs or symptoms:
- vomiting that lasts more
than two days
- you are unable to keep
liquids down for more than a day
- diarrhoea that lasts for
more than three days
- blood in your vomit
- blood in your stools
- seizures (fits)
- changes in your mental
state, such as confusion
- double vision
- slurred speech
- signs of severe dehydration,
such as a dry mouth, sunken eyes and an inability to pass urine, or
passing small amounts of dark, strong-smelling urine.
Always contact your
doctor if you get food poisoning during pregnancy. Extra precautions may be
needed.
Preventing food poisoning
The best way to avoid
getting food poisoning is to ensure you maintain high standards of
food hygiene when storing, handling and preparing food.
According to
the Food Standards Agency (FSA), a useful way of preventing food poisoning
is to remember the four Cs:
- cleaning
- cooking
- chilling
- cross-contamination (avoiding it)
You can prevent the
spread of harmful bacteria and viruses by maintaining good personal hygiene
standards and keeping work surfaces and utensils clean.
Regularly wash your
hands with soap and warm water, particularly:
- after going to the toilet
- after handling raw food
- before preparing food
- after touching bins
- after touching pets
You should
never handle food if:
- you are ill with stomach
problems, such as diarrhoea or vomiting
- you have sores and cuts
(unless they are covered with a waterproof dressing).
It is important to
cook food thoroughly, particularly poultry, pork, burgers, sausages and
kebabs. This will kill any harmful bacteria that may be present, such as
listeria and salmonella.
Make sure the food is
cooked thoroughly and is steaming hot in the middle. To check that meat is
cooked, insert a knife into the thickest or deepest part. It is fully cooked if
the juices are clear and there is no pink or red meat. Some meat, such as
steaks and joints (but not rolled joints) of beef or lamb, can be served rare
(not cooked in the middle), as long as the outside has been cooked properly.
When reheating food,
make sure it is steaming hot all the way through. Do not reheat food
more than once.
Certain foods need to
be kept at the correct temperature to prevent harmful bacteria from growing and
multiplying. Always check the storage instructions on the label.
If food has to
be refrigerated, set your fridge to 0–5°C (32–41°F).
If food that needs to
be chilled is left at room temperature, bacteria can grow and multiply to
dangerous levels.
Cooked leftovers
should be cooled quickly, ideally within 1–2 hours, and put in your fridge or
freezer. Dividing food into smaller amounts and putting it into
shallow containers will speed up the cooling process.
Cross-contamination
Cross-contamination
occurs when bacteria are transferred from foods (usually raw foods) to other
foods. Contamination can be:
- direct –
where one food touches or drips onto another food
- indirect –
where bacteria on your hands, work
surfaces, equipment or utensils are spread to food
To prevent
cross-contamination:
- always wash your hands after
handling raw food
- store raw and
ready-to-eat foods separately
- store raw meat in sealable
containers at the bottom of your fridge so that it cannot drip onto other
foods
- use a different chopping
board for raw food and ready-to-eat food, or wash it thoroughly in
between preparing different types of food
- clean knives and other
utensils thoroughly after using them with raw food
- do not wash raw meat or
poultry – any harmful bacteria will be killed by thorough
cooking, and washing may splash harmful bacteria around the kitchen.
Treating food poisoning
In most cases, food poisoning can be
treated at home without seeking medical advice.
It is very important
that you do not become dehydrated because it will make you feel worse
and slow down your recovery.
Dehydration is a
risk because you will lose fluid through vomiting and diarrhoea.
You should try to
drink as much water as possible, even if you're only able to sip it,
particularly after you pass diarrhoea.
Oral rehydration
salts (ORSs) are recommended for people vulnerable to the effects of
dehydration, such as the elderly and those with a pre-existing health
condition.
ORSs are available in
sachets from pharmacies. You dissolve them in water to drink and they help
replace salt, glucose and other important minerals your body loses through
dehydration.
If you have a kidney
condition, some types of oral rehydration salts may not be suitable for you.
Ask your pharmacist or family doctor for further advice about this.
To cope with your
symptoms and speed up your recovery you should also:
- rest
- eat when you feel up to it
(the gut sometimes needs time to recover and food may cause diarrhoea
even if you feel better)
- stick to foods that are
easily digested, such as toast, crackers, bananas and rice until you begin
to feel better
- avoid alcohol, cigarettes,
caffeine and spicy and fatty foods because they will make you feel
worse.
Visit your doctor or accident and emergency (A&E) department if you are severely
dehydrated – for example, if you have sunken eyes and you are unable
to urinate.
Your
doctor may admit you to hospital so that you can be given fluids and
nutrients through a tube inserted into a vein (intravenously).
Antibiotics may
be prescribed if test results show the source of your food poisoning was
bacterial, and your symptoms are severe or last longer than 3–4 days.
Antibiotic
tablets are usually used, although you may be given injections if your
symptoms are severe or if you are struggling to keep tablets down.
Source: NHS Choices.
Source: NHS Choices.