Why do some foods cause diarrhea

Food poisoning and infectious diarrhea

Infectious diarrheal diseases(Infectious gastroenteritis, colloquially also called gastrointestinal flu or vomiting diarrhea): Gastrointestinal inflammation caused mainly by viruses and bacteria, more rarely caused by parasites, with severe diarrhea, often with abdominal pain, nausea and vomiting.

Food poisoning: Diarrhea caused by toxins in food that has been spoiled by bacteria.

Diarrhea pathogens are usually transmitted through contaminated food or direct contact with sick people. Most of those affected get well again without therapy - it is especially important that fluid losses and minerals are balanced out. This is especially true for infants, toddlers and the elderly.

If there is also a high fever or the diarrhea is bloody, treatment with antibiotics is sometimes necessary, for example if a Salmonella infection is detected.

Leading complaints

  • Evacuation of misshapen, soft to watery stool several times a day
  • (Crampy) abdominal pain
  • Possibly nausea and vomiting
  • Occasionally fever
  • Possible admixture of mucus, blood or pus with the stool.

When to the doctor

The next day if

  • the diarrhea lasts more than three days.

Today if

  • You are very weak, dizzy, or have collapsed.
  • the diarrhea is bloody or purulent and has a high fever (over 39 ° C).
  • severe diarrhea occurs after a long-haul trip.

The illness

Overview: Infectious Diarrhea

In the case of infectious diarrhea, pathogenic viruses, bacteria, parasites or (very rarely) fungi get into the intestines through smear infection or the consumption of contaminated food. Secretory diarrhea, in which more water-absorbing substances are released into the intestine, is typical of these infections. If body water flows passively into the intestine, the intestinal contents liquefy and diarrhea occurs. Loss of fluid is particularly dangerous for children and the elderly: the high fluid loss causes them to dry out so much that there is a risk of circulatory collapse.

It is often underestimated how quickly infectious diarrhea is transmitted. Affected people excrete the pathogens en masse with the stool and pass them on to the hands via the smallest remnants of stool, e. B. when shaking hands (smear infection). Many diarrhea pathogens are also very stable outside the human body, stick to door handles, fittings or shared towels and are thus transmitted to other people. That is why thorough hand washing is a top priority in the case of diarrheal diseases!

Viral diarrhea

Viral diarrhea(Viral gastroenteritis). Viruses like Rota- or Noroviruses are the most common cause of infectious diarrhea, e.g. B. Rotaviruses cause 70% of diarrhea in children. The diarrhea is often accompanied by abdominal pain, nausea, and vomiting. Many patients also have a slightly elevated body temperature. Viral diarrhea is mostly harmless in our country, but is a major cause of high child mortality in developing countries with poor medical care.

Noroviruses are particularly contagious. Even the smallest amounts of virus-containing substances that are invisible to the eye are sufficient for infection. Relatives and carers can therefore become infected via droplets in the air, e.g. B. when patients vomit like a gush. At best, those who take care of those affected wear face masks and nasal masks.

Bacterial diarrheal disease

Bacterial diarrhea (Bacterial gastroenteritis) occur less often than virus-related diarrhea. But the clinical picture is often more severe:

  • Salmonella infection (Salmonella enteritis, salmonellosis): Salmonella bacteria cause vomiting, diarrhea, abdominal cramps and fever and are the most common cause of bacterial intestinal diseases in our latitudes. Typical sources of infection are insufficiently heated animal foods, e.g. B. raw or soft-boiled eggs and egg dishes (e.g. tiramisu), raw or insufficiently heated poultry meat, mussels or minced meat. While the pathogens with long enough heating (at least 70 ° C or 50 ° C over 1 hour) are killed, the pathogens keep for a very long time at low temperatures, even in the freezer. Salmonella are particularly dangerous for children and the elderly: due to the high loss of fluid, they dry out so much that there is a risk of circulatory collapse.
  • E. coli bacteria. Some diarrhea pathogens can be particularly dangerous because they produce toxins in the intestines, the so-called enterotoxins. Common representatives of these toxin-producing bacteria are:
  • enterohemorrhagicE. coli bacteria (EHEC). Don't always cause EHEC infections Complaints. In addition to raw meat and raw milk products, people who carry the pathogen but do not develop any symptoms are typical sources of infection. EHEC is particularly dangerous in young children, the elderly and immunocompromised people. They then suffer from (bloody) watery diarrhea, severe abdominal pain and fever. A dreaded complication is hemolytic uremic syndrome (HUS), which can lead to the breakdown of red blood cells and severe bleeding up to acute kidney failure. Even with timely therapy, HUS is fatal in 2% of cases.
  • enterotoxin-producing E. coli bacteria (ETEC) are responsible for around 40% of traveler's diarrhea. How dangerous an infection with ETEC is depends on how many of the pathogenic bacteria are in the intestine. The higher the number of pathogens, the more toxins are produced. As a result, there is a risk of long-term complications such as kidney damage and thus high blood pressure.

Parasitic diarrheal diseases

  • Parasitic diarrheal diseases (parasitic gastroenteritis, PGE): Every child in the tropics grows up with them - fortunately, they are less common here. The more common pathogens include:
  • Giardia(Giardiasis, Lamblienenteritis): The unicellular organisms are v. a. Widespread in the tropics, however, they can in principle be found anywhere in the world and are transmitted faecal-orally. The disease is also a zoonosis, so it can be transmitted from animals to humans (e.g. cats, cattle). An infection can be completely symptom-free, but it can also cause severe abdominal pain, fever and diarrhea.
  • Amoebic dysentery. Few species of amoeba cause health problems. The sometimes difficult amoebic dysentery is only triggered by the rather rare Entamoeba histolytica. The source of infection is v. a. Drinking water or food contaminated with feces is an option. The invasive form of the amoebic dysentery occupies a special position: intermediate stages of the amoeba (trophozoites) migrate from the intestinal space into the body and cause colon ulcers and abscesses in the liver.

Food poisoning

  • At Food poisoning the diarrhea will not go through Pathogens caused by themselves, but by theirs Toxins (Toxins). These are formed by the bacteria and ingested by humans with spoiled food. Common representatives of bacteria are Staphylococcus aureus, Bacillus cereus and Clostridium perfringens. Food poisoning is suspected if the symptoms appear suddenly (after 1–16 hours) and several people become ill at the same time after eating the same food. Typical complaints are nausea, violent vomiting, diarrhea and abdominal cramps, and there is usually no fever. Symptoms usually subside after 1 to 2 days.

Food poisoning caused by the poison of the bacterium is very rare, but life-threatening Clostridium botulinum, the botulinum toxin. Even after the ingestion of the smallest amounts, after initial vomiting and diarrhea, it leads to neurological deficits such as swallowing, speech and vision disorders, especially double vision. In the most severe cases, the poisoning leads to respiratory paralysis and death (botulism). Sources of infection are inadequately sterilized or not airtight packaged canned food or jars with smoked food or sausage, sometimes easy to recognize by inflated lids.

Diagnostic assurance

A thorough medical history, the clinical examination, is usually sufficient for the doctor to make a diagnosis. A microbiological stool diagnosis and / or a blood test for certain diarrhea pathogens is only recommended in special cases, e.g. B. at

  • Severe clinical picture, fever
  • Bloody stool
  • Travel history (i.e. if the patient has been abroad)
  • People from community facilities and food processing companies
  • Suspected epidemic.


On the basis of the clinical examination and the overall impression, the doctor decides whether the patient can treat himself, whether he needs (further) visits to the doctor or whether a hospital admission is necessary. This is advisable in the case of bloody or purulent diarrhea, high fever and severe impairment of the general condition. In babies and small children, too, replacing fluids and minerals is often only possible in the form of infusion therapy in the clinic.

Home therapy

If treatment at home is justifiable, it mainly consists of the supply of fluids and minerals (more on at-home hydration and regeneration therapy below). In addition, the doctor prescribes medication to counter nausea (anti-emetics) in the event of severe vomiting. For certain emergencies, e.g. For example, if you have a flight, your doctor may recommend anti-motility drugs such as loperamide. These inhibit the movement of the bowel and thus the diarrhea - but they also slow down the elimination of the diarrhea pathogens and prolong the healing process.

Inpatient therapy

Inpatient therapy also focuses on the necessary replacement of fluids and minerals, mostly in the form of ready-to-drink salt solutions (e.g. Elotrans®), sometimes also as electrolyte solutions via an infusion, due to the initially lacking precise diagnosis. As a check, the doctor will order repeated blood tests to check the electrolytes and hematocrit. Often, however, an antibiotic is given as an infusion before the microbiological test results are received. As soon as the results of the microbiological blood and stool samples are available, the doctor adjusts the therapy if necessary.

Reporting requirement

Infectious gastroenteritis is one of the notifiable diseases. Is z. If, for example, a person is concerned who is employed in a restaurant, kitchen or in the food processing industry, the doctor must pass on suspicion of food poisoning or infectious gastroenteritis to the health department. The doctor must also report if certain pathogens are detected. Notifiable pathogens include: B .:

  • Rotavirus
  • Norovirus
  • certain E-coli bacteria
  • Salmonella
  • Shigella.


In most cases, infectious diarrheal diseases heal well with rest, fluid replacement and nutritional supplements. Due to the greater risk of dehydration, rapid fluid replacement is important, especially for old people and children.

In the case of food poisoning with botulinum toxin, which is fortunately very rare, the mortality of intensive care patients is less than 10%. If left untreated, however, up to 70% of infected patients die.

Your pharmacy recommends

What you can do yourself

Drink a lot. Those who have diarrhea have to drink a lot to make up for the loss of water and salts. Tea preparations made from dried blueberries, blackberry or raspberry leaves are recommended. They contain tannins that protect the intestinal mucosa. Diluted chamomile or peppermint tea are also suitable. An alternative is sugary lemonade diluted with water. For more severe diarrhea, however, salt-sugar solutions are the better alternative. The drinking solution of the World Health Organization (WHO drinking solution) is easy to make yourself: one liter of water is mixed with 13.5 g glucose, 2.9 g sodium citrate, 2.6 g sodium chloride and 1.5 g potassium chloride. Ready-made granules from the pharmacy are also particularly suitable for travel.

Medicinal charcoal (Charcoal Compretten® tablets, charcoal Hevert® tablets). By taking activated charcoal, harmful substances (e.g. bacteria, toxins) are removed from the body and excreted in the stool. Its effectiveness is sometimes questioned by conventional medicine, but many sufferers have had good experiences with it.

Note: Taking medicinal charcoal (activated charcoal) reduces the effect of many orally taken medications, e.g. B. also those of antibiotics and also those of the "pill". If in doubt, ask the doctor whether it is sensible and justifiable to take it.

Food leave. It is controversial whether it is advisable to forego eating altogether in the acute stage. The fact that the damaged intestinal mucosa is not additionally irritated speaks in favor of a temporary abstinence from food. It is best to use your appetite as a guide: if the thought of eating makes you uncomfortable, don't eat. However, if you are hungry, use the BRAT diet with bananas, rice, applesauce and toast.

No dairy products. Avoid dairy products. In the case of diarrhea, the effectiveness of the lactose-breaking enzyme is often limited, so that symptoms of milk intolerance can temporarily occur.

Build-up diet. If you feel your appetite again, a light diet is recommended. Are suitable for this purpose, for. B. vegetable broth, rice gruel, but also pretzel sticks, crackers or rusks. For the rice gruel, boil two tablespoons of rice in one liter of lightly salted water until a thin gruel has formed. Now add two tablespoons of oatmeal and cook for another 15 minutes. Then let the rice gruel cool down and then consume it slowly in small portions throughout the day.

Hygiene. In order not to infect others, strict hygiene is required. This means thorough hand washing after every use of the toilet and after caring for a sick person. Remove vomit with gloves and wash bedclothes, towels and pajamas, preferably at 60 ° C, to kill pathogens.


Infection. Some pathogens are even excreted when the person concerned no longer feels sick himself. This is especially the case with noroviruses and EHEC. You should therefore pay attention to meticulous hand hygiene for a few more days after infectious diarrheal diseases.

At home. Attention to hygiene and shelf life are also essential when it comes to the preparation and storage of food in the fight against infectious diarrheal diseases. Meat, poultry and eggs should be cooked for a long time and at high temperatures. Salmonella survive freezing temperatures; therefore, frozen poultry and meat must be carefully washed before preparation and all objects that come into contact with them must be thoroughly cleaned.

As far as possible, avoid raw or half-cooked meat, raw fish and raw seafood, raw or soft-boiled eggs, dishes prepared with raw eggs (e.g. tiramisu) and canned food with a blown lid.

Vaccination. Since rotaviruses are the most common cause of gastrointestinal infections in children under five years of age, the Standing Vaccination Commission (STIKO) recommends a rotavirus vaccination for infants. This is given as an oral vaccination; the series of vaccinations should begin at the age of six to twelve weeks and, depending on the vaccine, be completed by the age of 24 or 32 weeks. The vaccination can be given together with other standard vaccinations for infancy.

Complementary medicine

Herbal medicine. Dried blueberries help against diarrhea, also as a tea infusion. They contain many tannins that protect the intestinal mucosa. Tea made from blackberry leaves or black tea has a similar effect.

Herbal medicine recommends standardized dry extracts, for example from apple powder (Aplona® apple powder), bloodroot (bloodroot ratiopharm® capsules) or oak bark (e.g. Traxaton® tablets).


Dr. med. Arne Schäffler, Dr. Bernadette Andre-Wallis in: Health Today, edited by Dr. med. Arne Schäffler. Trias, Stuttgart, 3rd edition (2014). Revision and update: Dr. med. Sonja Kempinski | last changed on at 14:50

Important note: This article has been written according to scientific standards and has been checked by medical professionals. The information communicated in this article can in no way replace professional advice in your pharmacy. The content cannot and must not be used to make independent diagnoses or to start therapy.