Saccharomyces boulardii is a non-pathogenic, non-colonizing yeast that has been shown to have probiotic effectiveness in some clinical applications. It is a hardy microorganism that can survive gastric acidity and is not adversely affected or inhibited by antibiotics. Although some manufacturers substitute S. cerevisiae (bakers yeast) for S. boulardii in their product formulations, Klaire uses only certified S. boulardii organisms to ensure maximum potency and effectiveness. Although lactose is typically used in S. boulardii products, Klaire uses lactose-free, gluten-free material. This hypoallergenic formulation is available in vegetarian capsules.