When to use it: When you are not near your own bathroom and can’t let a case of diarrhea subside naturally.
What it does: This ingredient (also known as pink bismuth) is found in over-the-counter products, like Kaopectate and Pepto-Bismol, and doubles as an antacid and an anti-inflammatory. It works, and sometimes too well: A common side effect is constipation. “Most diarrhea just needs to run its course,” says Weiss. “It’s best to let it clear up on its own.” (Note: This medicine should not be given to children. Salicylates, in rare cases, have been shown to cause Reye’s syndrome.)