What is foodborne illness (food poisoning)?
Foodborne illness (or food poisoning) is any illness caused by eating or drinking contaminated food or liquids including water. Most infectious contamination of food is caused by bacteria, viruses, or parasites. These are also called germs or bugs. Harmful toxins and chemicals can also contaminate food and cause foodborne illness (intoxication).

A.    Bacteria causes:

B.    Viral causes:

C.    Parasitic causes:

D.    Intoxications:

How does foodborne illness (food poisoning) happen?
Bacteria (germs):

Food poisoning can happen when bugs and germs called bacteria are allowed to get onto food or drink. If someone eats food with lots of bugs on it, they can get food poisoning. When food poisoning is caused by bacteria, they can grow on the food and make food poisoning even worse.  If there are a lot of bacteria on food it can make the person who eats it very unwell, meaning they may need to go to hospital or that they may even die. Vulnerable people who are less able to fight off infection.  Vulnerable people including small children, very elderly people, people who have had major surgery recently, people living with cancer, can get very unwell from food poisoning.

If bacteria (germs) are allowed to get onto food or drink, they can grow very quickly. For example, bacteria called salmonella can grow from one germ into billions in just one day if left on food like raw or undercooked meat, poultry, eggs, or milk.

Viruses (germs):

A different type of germs called viruses can also cause food poisoning. Viruses do not grow on food like bacteria. Instead they grow inside the body of the person who has eaten the food with a virus on it.  

Many foodborne illnesses are notifiable diseases in Ireland. 

What are the symptoms of foodborne illness (food poisoning)?
The symptoms of food poisoning are different for different germs. Fortunately, most forms of food poisoning last only a short time - between 1 and 3 days. Sometimes a person may feel sick for longer than a week, and in the most extreme cases, food poisoning can cause death.

The types of symptom that people usually get when bacteria causes food poisoning is called gastroenteritis. Gastroenteritis symptoms are nausea (feeling like getting sick), vomiting (throwing up/being sick), diarrhoea. Other symptoms of food poisoning can be abdominal (stomach) cramps, fever (a high temperature) and headaches.

If someone gets typhoid or paratyphoid food poisoning they usually get a fever, aches, constipation, and flu like symptoms. Diarrhoea is less common with typhoid and paratyphoid food poisoning. 

Food poisoning from viruses usually causes vomiting rather than diarrhoea.

Although symptoms of infection with protozoa vary widely, they usually cause heavy watery diarrhoea.

Depending on the toxin, food poisoning caused by toxins (intoxication) can produce a wide range of symptoms from flu like illness to muscle weakness and paralysis (not being able to move your body).

How is food poisoning managed?
Most of the time, food poisoning causes symptoms which last 1 to 3 days and can be managed at home. Food poisoning caused by some germs (bacteria) can cause symptoms which last a week. Salmonellosis, cryptosporidiosis, VTEC and campylobacteriosis generally cause symptoms which last for a week.

If someone has diarrhoea or vomiting from food poisoning it is important that they drink plenty of fluids to prevent dehydration (not having enough water in the body). Drinking plenty of fluids, resting and eating small bland meals is usually the best approach. To stop others from getting sick, it is important to stay off school or work until you have not been sick or had diarrhoea for at least 2 days.

Antibiotics and anti-diarrhoeal medication are not normally needed to treat food poisoning. Very rarely a severe case of bacterial infection (e.g. typhoid) will require antibiotics but this is the exception.

Speak to your GP if:

  • you're worried about a baby under 12 months old
  • your child stops breast or bottle feeding while they're ill
  • a child under 5 years has signs of dehydration - such as fewer wet nappies
  • you or your child (over 5 years) still have signs of dehydration after using oral rehydration sachets - signs of dehydration, include little or no urination (peeing), a very dry mouth and throat, or feeling dizzy when standing up
  • you or your child keep being sick and cannot keep fluid down
  • you or your child have bloody diarrhoea or bleeding from the bottom (bum)
  • you or your child have diarrhoea for more than 7 days or vomiting for more than 2 days


How can food poisoning be prevented?
The following are the best methods to prevent food poisoning: 

  • Handwashing: always wash your hands with soap and running water and especially:
    • after using or cleaning the toilet
    • after attending to anyone with diarrhoea or vomiting
    • after touching anything contaminated by diarrhoea or vomiting
    • after handling contaminated clothing or bedding (including nappies)
    • after handling household and garden waste or rubbish
    • after touching or handling pets or other animals
    • on returning to the house having been working in the garden or on the farm
    • before handling, preparing, serving, or consuming food or drink

Proper handwashing means following these five steps:

  1. Wash
  2. Soap
  3. Rub between fingers, thumbs and all parts of the hands for at least 20 seconds
  4. Rinse
  5. Dry

Teach kids how to wash their hands using Safefood resource

  • Cleaning: utensils and surfaces should be kept clean at all times, especially before being used to prepare food and if anyone in the house is sick.
  • Cooking: food should be cooked properly and according to the manufacturer's instructions.
  • Prevent cross contamination: raw and cooked (ready to eat) food must be kept separate - juices from raw food should not be allowed to drip on cooked food in a fridge.
  • Refrigeration: cooked and raw food must be kept in the fridge - this is especially true for meat and dairy produce. Ensure your fridge is working properly. Five degrees Centigrade (5 °C) is the temperature that food should be stored at in the fridge.

Further information on storing and preparing food can be found at safefood.net.

Updated 28th November 2022