How does Pepto-Bismol cause black diarrhea?

Turns out this is a very common side effect of Pepto Bismol. The active ingredient in Pepto Bismol is bismuth salicylate that helps alleviate heartburn and gastrointestinal discomfort. However, bismuth when combined with trace amounts of sulfur present in your saliva and gastrointestinal tract forms bismuth sulfide that is black in color. read more

A small amount of a substance called sulfur is present both in saliva and in the gastrointestinal tract. Sulfur interacts with bismuth, the active ingredient that's used in Pepto-Bismol. The result is a new substance called bismuth sulfide, which is what causes the stool to turn black. read more

Pepto is indicated to treat diarrhea and traveler’s diarrhea. A common cause of diarrhea is a virus or bacteria, but it could also be caused by eating foods that upset the digestive system. Diarrhea Relief . When you take Pepto as soon as you start experiencing diarrhea symptoms, it can help provide relief when you need it most. read more