Children younger than age 12 who have significant diarrhea should not use bismuth subsalicylate, and children under age 6 should not use loperamide. Instead, children under these ages who experience persistent diarrhea should be taken to a physician for medical care. Children with viral infections such as chickenpox or influenza should not take bismuth subsalicylate because of an increased risk of developing Reye syndrome, a condition in children associated with the use of aspirin and other salicylates that results in brain and liver damage.

Fluid loss caused by diarrhea can present serious health risks in children, and antidiarrheals can sometimes mask this dehydration. Fluids, including oral electrolyte solutions, can prevent dehydration. Older children with diarrhea may use antidiarrheals, but it is important that they also receive sufficient fluids to prevent dehydration.