Probiotics are microorganisms.

They are believed to be beneficial for the gastro-intestinal system via suppression of some of the harmful microorganisms responsible for infections of the gastro-intestinal tract.

Probiotics are not effective in combating all the harmful microorganisms which cause diarrhea.

Medications may therefore be needed to prevent conditions such as traveler's diarrhea.

Bismuth subsalicylate (Pepto Bismal) can help prevent Escherichia coli (E.coli) and viral stomach illnesses. Bismuth is not recommended for children. Children's Pepto's active ingredient is calcium carbonate (chalk). Bismuth is element 83 in the periodic table of elements.