Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Stop taking  bismuth subsalicylate and call your doctor at once if you have:
changes in behavior with nausea and vomiting;
hearing loss or ringing in your ears;
diarrhea lasting longer than 2 days; or
worsened stomach symptoms.
Bismuth subsalicylate can cause you to have a black or darkened tongue. This is a harmless side effect.
Common side effects include:
constipation; or
dark colored stools.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Bismuth subsalicylate side effects (more detail)
