Saccharomyces boulardii is a non-pathogenic yeast strain that has been used for treatment and prevention of diarrhea. Saccharomyces boulardii is classified as a "probiotic," or a microorganism that when ingested may have a positive influence on the host's health. Probiotics may exert their effects on the gastrointestinal system directly, or may modulate the immune system in a larger scope. Human studies indicate Saccharomyces boulardii may prevent antibiotic-associated diarrhea, Clostridium difficile diarrhea in combination with antibiotic therapy, diarrhea associated with tube feeds, and acute childhood diarrhea. Promising initial studies have shown that Saccharomyces boulardii may be beneficial in treating diarrhea associated with HIV. The German Commission E has approved the use of Saccharomyces boulardii for symptomatic treatment of acute diarrhea, prophylactic and symptomatic treatment of diarrhea during travel, treatment of diarrhea occurring while tube feeding, use as an adjuvant for chronic acne, for a dietary supplementation, and for a source of B vitamins and protein.