Severe drowsiness is a side effect of Pepto-Bismol, according to Drugs.com. Other severe side effects some people experience include allergic reactions, nausea, vomiting and severe constipation. Additional serious side effects include fever, hearing loss and ringing in the ears. Severe allergic reactions experienced include itching, rash, hives, tightness of the chest and difficulty breathing. Users also may experience swelling of the mouth, tongue, lips or face. Common side effects are a temporary darkening of the tongue or stool.
Experiencing side effects from Pepto-Bismol tablets is rare, and they usually stop when users stop taking the medication, notes WebMD. Users who experience severe reactions should immediately seek medical attention. Experiencing continuous vomiting or diarrhea may lead to dehydration. Symptoms of dehydration are dizziness, rapid heartbeat, unusual thirst and decreased urination.
Very rare side effects are bleeding from the stomach or intestines, explains WebMD. Symptoms of these side effects are black or bloody bowel movements, abdominal pain, and dark, grainy vomit. Taking Pepto-Bismol tablets to treat the symptoms of a viral infection, such as the flu, can cause Reye's syndrome in children and teenagers, according to Drugs.com. Children are more susceptible to experience side effects. Pepto-Bismol tablets are to be taken as directed for no more than 48 hours at a time.