Stop use and ask a doctor if: 1 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. irritation, pain, or redness persists or worsens. 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. Ask a doctor before use if you have: persistent or chronic cough such as occurs with smoking, asthma, or emphysema cough accompanied by excessive phlegm (mucus).