Saccharomyes boulardii is a yeast probiotic. S. boulardii has many mechanisms of action including inhibition of some bacterial toxins, anti-inflammatory properties, the ability to stimulate the intestinal mucosa to increase brush-border enzymes, as well as immunostimulatory effects.

There is evidence that S. boulardii is beneficial for the treatment of acute gastroenteritis and recurrent infections, as well as for the prevention of antibiotic-associated diarrhea. S. boulardii has been researched in children and infants and has been demonstrated to be a treatment option and used for prevention of infantile gastroenteritis and antibiotic-associated diarrhea.