Saccharomyces boulardii is a non-pathogenic probiotic yeast that protects against antibiotic-associated diarrhoea caused by a disruption in the balance of healthy gut flora. It is resistant to local stresses, including digestive enzymes, bile salts, organic acids, and variations in temperature and pH. As Saccharomyces boulardii is also naturally resistant to antibiotics, it can be taken by individuals receiving antibiotics to nutritionally support the gastrointestinal tract by maintaining gut flora balance. Randomized, placebo-controlled clinical trials, each involving hundreds of adults taking antibiotics, have demonstrated a significant preventive effect on the occurrence of diarrhoea. Furthermore, Saccharomyces boulardii is the only probiotic reported to have significant efficacy in reducing relapsing C. difficile-associated diarrhoea, which is responsible for approximately 10-20% of antibiotic-associated diarrhoea cases. Each capsule of Saccharomyces boulardii contains 5 billion colony forming units (CFU).