Food poisoning


Food poisoning


Keywords: Inflammation of stomach and intestine, diarrhoea, vomiting, nausea

​Food poisoning, i.e. a sudden inflammation of the bowel, is a very common food- and waterborne disease. The symptoms are caused by viruses, bacteria, protozoans or toxins. Food poisoning usually clears up in a couple of days and can be well treated at home.

Any sudden inflammation of the bowel caused by contaminated food or water is called food poisoning.  It is usually viral (e.g. norovirus), bacterial (salmonella) or a toxin generated by bacteria. Food poisoning can also be caused by chemicals, mushrooms, plants, parasites and animals.  The most common route of infection is food that has not been prepared, stored, produced or served properly, or drinking water. 

Vomiting without diarrhoea may be caused by some other abdominal condition, for instance stomach ulcers or intestinal obstruction. Severe long-term pain in the abdominal area is often associated with these conditions. Nausea and vomiting are common symptoms also with migraine, acute cerebral stroke, infections and diabetes. ​


​The symptoms of a food poisoning usually appear within a day from the exposure. Food poisoning caused by existing bacterial toxins in the food is symptomatic already in a couple of hours, while some bacteria or parasites take days or weeks before food poisoning symptoms emerge. One of the symptoms of inflammation of the stomach and intestine is always diarrhoea.  The definition of diarrhoea is having loose and watery bowel movements four or more times in 24 hours, or three times within eight hours. Other symptoms may include stomach cramps, vomiting and feeling sick. You may also have a high temperature.


​The most important treatment for food poisoning is to replace lost fluids by rehydration. Food and fluids are absorbed almost normally even in a case of severe diarrhoea. If you have food poisoning, you should drink several litres of fluids throughout the day. If you vomit a lot, taking small sips at a time may help.  The replacement of fluids and salts lost from diarrhoea is best done by a variety of beverages containing energy, such as diluted squash, water, tea, soup of berries and broth.  Milk-based, caffeinated drinks and artificial sweeteners are not recommended; avoid also energy drinks.

Eating will not make your condition worse as long as you have  something light and easy to digest. However, eating may give you stomach cramps or you may find eating impossible due to nausea and vomiting.  Do not have solids as long as you are vomiting, but sip fluids regularly and often, less than 1 dl at a time. If drinking is impossible due to nausea and vomiting, wait for an hour or two and then try again. Being sick or fasting for a couple of days is not harmful to adults.

Even if eating is simply impossible, you want to ensure sufficient intake of salts and could try rehydration solutions sold in pharmacies without prescription. Pharmacy staff will help you select the right product, if necessary. You can also prepare one at home: mix 1 litre of fruit juice (preferably orange juice) with 1 litre of water and 1 teaspoon of salt.  The natural sugar in the drink helps the water and salt to absorb. Special attention should be paid to sufficient hydration of the elderly because they are not always able to say if they are thirsty. If your urine is darker than normal, you may be dehydrated.

To prevent food poisonings, everyone of us can pay special attention to good hand and kitchen hygiene. Be meticulous with the correct storage and handling temperatures of foods as well as the appropriate washing and cleaning of storage and handling spaces. Check and observe the use-by dates, and refrigerate or freeze foods appropriately also at home.

When should you seek medical advice?

​You should seek medical advice, if

  • ​​the diarrhoea is severe and you have a temperature higher than 38.5°C.  
  • there are clear signs of blood in your stools or vomit. 
  • ​your general condition gets worse, you are exhausted, confused or disoriented, or your mucous membranes are constantly dry.
  • the symptoms continue over 7 days or high temperature for more that 4 days.
  • if the symptoms have started during travelling abroad or right after returning home
  • the symptoms include a severe headache, which is not caused by a known tendency to migraines.
  • ​vomiting gets more severe, you have stomach ache but no diarrhoea.​

If you suspect food poisoning from a specific foodstuff, water source or a place for dining, and if you know there are a number of infected people, report to your local health centre, whether you need medical advice or not. The food control authority shall investigate the possibility of an epidemic.​​

More information

The producers of the instruction

​​​​​Emergency care professionals have produced the instruction in collaboration with Terveyskirjasto.​


Updated  22.4.2021