S. Boulardii is the non-pathogenic yeast, Saccharomyces boulardii, which possesses probiotic activity that supports gastrointestinal health and immune function. This formula contains 500 mg (10 billion CFU) of S. boulardii per serving. This strain does not require refrigeration and has the ability to survive passage through the harsh gastric environment, withstanding high acidity, bile, and heat.