Pepto-Bismol turns the tongue black because the bismuth reacts with sulfur in saliva, forming harmless bismuth sulfide. It fades in a few days.
Why
Pepto-Bismol contains bismuth subsalicylate. Bismuth reacts with trace sulfur in your saliva and digestive tract to form bismuth sulfide, a black compound.
Effect
Harmless and temporary. The tongue and stool may turn black.
Duration
Fades within a few days of stopping.
Caution
Black stool from Pepto can look like bleeding. If you also have pain or tarry smell, see a doctor.
Avoid
Don’t use with aspirin allergy or give to children with flu.
The chemistry
Pepto-Bismol contains bismuth subsalicylate. In saliva and the digestive tract, trace sulfur compounds react with bismuth to form bismuth sulfide, which is black. This is harmless and temporary. The same reaction can turn stool black.
- The tongue color usually fades within a few days after stopping the medicine, typically 1 to 3 days.
- Brushing the tongue gently helps remove the stain.
- Each regular-strength dose contains about 262 mg of bismuth subsalicylate, and adults should not exceed 8 doses of 262 mg tablets (about 2,096 mg) in 24 hours.
Cautions
Bismuth subsalicylate contains salicylate related to aspirin. It should not be given to children or teens recovering from viral illness because of the risk of Reye syndrome. It also should be avoided by people allergic to aspirin or on blood thinners without medical advice. Black stool from the medicine can be confused with bleeding, so tarry, foul-smelling stool along with dizziness or abdominal pain needs medical attention. Ringing in the ears signals too much salicylate.
Chemistry
Pepto Bismol contains bismuth subsalicylate. In the gut, bismuth reacts with trace sulfur from saliva and the digestive tract to form bismuth sulfide, a black compound. This temporarily darkens the tongue and stool. The effect is harmless and clears within a few days after stopping.
Cautions
Black stool can also signal bleeding, so a person should consider the medicine as the cause only if they have taken it. The product contains salicylate, so it should not be given to children recovering from viral illness because of Reye syndrome risk, and people allergic to aspirin should avoid it. It can interact with blood thinners.
Chemistry in detail
Bismuth subsalicylate reacts with hydrogen sulfide produced by bacteria in the mouth and gut, forming black bismuth sulfide. Each 30 mL dose of regular liquid contains 525 mg of the compound. Black tongue and stool begin within a day and fade within 2 to 3 days after stopping.
Cautions
Do not take with aspirin or other salicylates unless a doctor agrees, and avoid with blood thinners such as warfarin. It should not be given to teenagers recovering from flu or chickenpox. Black tongue can also be hairy tongue, caused by overgrowth of papillae and bacteria, linked to smoking and antibiotics. A dentist can advise on brushing the tongue.
Based on data from the US Food and Drug Administration and the Mayo Clinic
