Irritable bowel syndrome (IBS) is one of the most prevalent gastrointestinal disorders affecting between 5 and 15% of the general adult population worldwide. Over the course of many years altered intestinal motility, visceral hypersensitivity, immune changes and, as it has recently been found, impaired epithelial barrier function were meant to explain the origin of symptoms in the IBS. We have come to realize now that the IBS warrants serious clinical and scientific study. Not that long ago, the connections between the gut and the brain have been expanded to include a new entrant, the microbiota, resulting in the creation of a new concept of a microbiota-gut-brain axis.Microbiota is a risk factor for the irritable bowel syndrome. Probiotics are defined as live microorganisms, which can alter the intestinal flora and regulate intestinal functions such as reduction of visceral hypersensitivity, improvement of mucosal barrier function, modulate immune responses and chronic inflammation, affect the central nervous system, gastrointestinal motility, etc. The correctness of this approach is confirmed by several studies of the probiotic Bifidobacterium longum subsp. longum 35624, which is widely used in the treatment of symptoms of irritable bowel syndrome. The dietary supplement Bifidobacterium longum subsp. longum 35624 contains 1 × 109 colony-forming units, which provides a clinically effective level of these beneficial bacteria. Bifidobacterium longum subsp. longum 35624 also reduces inflammation in the gastrointestinal tract and has positive results in reducing abdominal symptoms (e.g. abdominal pain / discomfort and bloating) associated with the irritable bowel syndrome and other conditions.