Acidophilus reduces the chance of getting traveler's diarrhea, the result of changes in intestinal flora. It is also useful for anyone who takes antibiotics, especially the broad-spectrum ones like tetracycline and ampicillin, which wreak havoc on intestinal flora, and it's useful for women who have frequent vaginal yeast infections. The dose is one tablespoon of the liquid culture or one to two capsules after meals unless the label directs otherwise. To treat yeast infection, you can also place the liquid culture directly in the vagina in addition to taking it by mouth. Always check the expiration date on acidophilus products. You want to be sure the bacteria in them are alive and in good condition.