Health questions answered: are over-the-counter cough syrups effective, and will they kill a cough?

No

Over-the-counter cough medications are convenient for people who have no time to visit the doctor and are looking for immediate comfort from chest congestion and a sore throat. Many think that these cough syrups are the answer to clearing up a cough, but this is not the case, says Dr Cheng Chor-ho, a family physician from Town Health Medical Centre in Hong Kong.

"Over-the-counter cough syrups cannot kill or inactivate the viruses that have caused the cough, nor can they suppress the cough," he says. "All they do is have a soothing effect on the throat."

Most cough mixtures bought over the counter contain cocillana, a herbal remedy to loosen phlegm; guaiphenesin, to relieve chest congestion; and

, to relieve a stuffy nose and clear sinuses. They are mild medications that can help relieve the discomfort from a minor cough and the common cold.

"But really, the best treatment for these ailments and other simple upper respiratory tract infections is adequate rest, coupled with plenty of fluids. Over time, your symptoms should improve," Cheng says.