Ask a doctor before use if you have: 1 persistent or chronic cough such as occurs with smoking, asthma, or emphysema cough accompanied by excessive phlegm (mucus). Keep out of reach of children. Sore throat warning: If sore throat is severe, persists for more than 2 days, is accompanied or followed by fever, headache, rash, swelling, nausea, or vomiting, consult a doctor promptly. These may be serious. Stop use and ask a doctor if: cough persists for more than 1 week, tends to recur, or is accompanied by fever, rash, or persistent headache. These could be signs of a serious condition. sore mouth does not improve in 7 days irritation, pain, or redness persists or worsens.