What causes diarrhea?

What causes diarrhea?

What causes diarrhea?


We talk about diarrhea when loose or liquid stool is donated more than 3 times a day. Diarrhea may be accompanied by increased body temperature, nausea, vomiting and general weakness and deterioration of well-being. Diarrhea most often occurs as a result of inflammation of the intestinal mucosa, but not only.


Some organisms react in this way to unfavorable combination of some dishes, e.g. plums with cream, cherries in larger quantities, sausage or pickled cucumbers with milk, etc. In other people diarrhea can cause severe stress or emotions (in addition, vomiting may also occur) .

These are causes not related to bacterial or viral infection. For the body to “recover”, it is enough to drink a summer tea made of mint, chamomile, lemon balm or calendula and a bit of starvation.

Diarrhea can also be accompanied by indigestion caused by eating a heavy meal (usually late in the evening). There are, however, much more serious reasons that should not be underestimated.

These include: infectious diarrhea, allergic reactions, irritable bowel syndrome, ulcerative colitis, Crohn’s disease, hyperthyroidism, cancer, alcohol abuse, an overdose of vitamin C or magnesium, and side effects of medications.

Infectious diarrhea

Acute infectious diarrhea can be caused by bacteria, viruses, protozoa or pathogenic fungi. Bacteria that most often contribute to upset include: Campylobacter jejuni (infection increases in spring), salmonella and shigella (bacterial dysentery) – poisoning most often occurs in the summer months – and Yersinia enterocolitica – most cases occur in winter.

As a result of the weakening of the body, the patient often falls into so-called intestinal flu. It is caused by rotaviruses (infections in children) and noroviruses that affect adults. Infectious diarrhea can be infected through contact with a sick animal or person and consumption of contaminated food or water (most often it is unpasteurized milk, eggs or meat from sick animals).

The stool is liquid or semi-liquid and may contain a large admixture of mucus, pus and even blood. In most cases, even acute infectious diarrhea gradually goes away on its own, thanks to the functioning of the human immune system. Frequent replenishment of fluids and electrolytes, e.g. Orsalit, is important to prevent dehydration. How long does infectious diarrhea last? Depending on age and immunity, about a week. In more severe cases, it may extend to 10 days or require hospital treatment.

Protozoal infection


In people with reduced immunity, diarrhea is most often caused by Giardia lamblia (lambliosis) and Cryptosporidium parvum (cryptosporidosis). Protozoa belong to independent unicellular organisms that have the ability to move.


The development of Giardia lamblia is characterized by two phases – cysts (spore form) and trophozoite (growth and nutrition phase). Accordingly, oocytes and sporozoites are distinguished in the development of Cryptosporidium parvum. After ingestion of Giardia lamblia cysts, 2 trophozoites are released in the small intestine, and Cryptosporidium parvum oocytes – 4 sporozoites.

They attach to the surface of the intestinal mucosa and intensively multiply through division, causing disease symptoms. Both lambliosis and cryptosporidosis can be asymptomatic, acute, subacute, chronic or recurrent. A common feature of both diseases is watery diarrhea.

It may be accompanied by: fatigue, insomnia, lack of appetite, headache and stomach ache, nausea, flatulence or vomiting (protozoa damage the intestinal mucosa, thereby impairing the absorption of fats, vitamins A and B12, folic acid and lactose). If the parasites attack further parts of the digestive system, the symptoms are usually accompanied by cholangitis, pancreatic irritation and jaundice.

Infection can occur through the oral route, as a result of eating undercooked meat containing protozoan cysts or by contact with an infected person. The source of infection may also be contaminated ponds, rivers and streams.

Cysts can survive in the intestine of flies for one to two days, and in moist soil even for several months. That is why it is so important to wash your hands and fruits and vegetables thoroughly before eating. Diarrhea caused by invasion of protozoa requires treatment with appropriate imidazole preparations such as metronidazole or nitazoxanide.

Pathogenic fungi and diarrhea

Mycoses are more commonly affected by children and the elderly with reduced immunity, treated with immunosuppression, taking anticancer drugs, corticosteroids, patients after antibiotic therapy, parenteral nutrition and suffering from diabetes. Gastrointestinal candidiasis is most often caused by candida albicans, which live in the digestive tract in about 40% of the population.

When they are few, they do not cause disease symptoms, but when the body is weakened, they multiply strongly, causing various ailments. Untreated candidiasis can damage the intestinal epithelium and overload the liver and kidneys.

The first symptom is chronic fatigue syndrome, bloating, rashes, abdominal pain, digestive problems, followed by halitosis. Treatment of fungal infection of the digestive system is extremely difficult and slow. In addition to pharmacological agents, probiotics play a key role, increasing immunity.

Food alergy

Allergy to some foods can cause vomiting, colic, bloating, stomach ache and diarrhea after eating. Such foods include, among others: cow’s milk, eggs, tomatoes, strawberries, kiwi, celery, cocoa, chocolate, honey, fish, nuts, rice, citrus fruits and soybeans. The treatment of food allergy is difficult because it usually affects several products that need to be identified.

For this purpose, the elimination diet is most often used. Once an allergen-containing product is detected, it should be avoided, but it cannot be completely excluded from the diet. The use of preparations supporting the work of the immune system is very helpful in treatment.

Diarrhea associated with such diseases as sensitive bowel syndrome, ulcerative colitis, Crohn’s disease, hyperthyroidism or cancer is difficult to treat. After eliminating the main disease, it usually disappears on its own.