Acute exposure of the gastrointestinal tract to pathogens, toxins, allergens, and xenobiotics (pesticides, radionuclides, salts of heavy metals, etc.) can result in development of gastrointestinal infections, intoxication and allergic reactions. Vital bodily functions are associated with the production of harmful and toxic metabolites. Part of them having reached the gut are usually eliminated from the body with faeces, but some of harmful substances may be reabsorbed into the bloodstream again and transported back to the liver, remaining in the enterohepatic circulation. The most common symptoms of acute intoxication include a feeling of general malaise, headache, nausea, vomiting, diarrhoea, allergic manifestations, and elevated body temperature.