Acute coughs cost the UK economy almost £1 bn every year, experts warn.
More research is needed into the cause of coughs
The British Thoracic Society said there was little evidence over-the-counter medicines had any specific pharmacological effect on acute coughs.
It also warned research was needed into the causes of chronic cough - also a significant problem.
The society has published guidelines in the journal Thorax to help doctors distinguish between the two forms of the condition.
Lasts less than three weeks
Usually associated with viral upper respiratory tract infection
Normally self-limiting and benign
Can occasionally sometimes be the first indication of a more serious condition in the absence of other significant symptoms
According to the society, acute coughs cost the UK economy £875 million a year in lost productivity, on top of £104 million healthcare costs.
Patients often report that they derive some benefit from taking cough medicines.
But the BTS experts said while there was evidence to suggest that medicines can suppress a cough, there was little to show that they effectively treat it.
No obvious cause
Chronic cough is often caused by asthma, drugs, environmental triggers or heartburn - but in a quarter of cases it cannot be attributed to a specific cause.
Professor Ian Pavord, who oversaw the formulation of the new guidelines, said: "Chronic cough is a common condition which is currently under-researched.
Lasts more than eight weeks
Often caused by asthma, drugs, environmental triggers or heartburn
Most common in middle-aged women and obese people
Reported by 10-20% of adults
"While an attempt is being made to understand the condition and create better diagnostic protocols and treatments, there are still a significant number of patients who we can't help with specific treatment.
"It is important for healthcare professionals to use objective measures of cough severity when evaluating the effects of drugs and other treatments for chronic cough.
"New diagnostic tools are being produced all the time, but there is still some way to go."
He said one method of recording a cough over at least 24 hours - "ambulatory cough recording" - seemed to be the best method of measuring its severity.
Professor Peter Barnes, an expert in thoracic medicine at London's Imperial College, agreed that cough was major problem.
"It is the commonest symptom for which people go to see their doctor," he said.
"There is a need to find out more about why people get chronic cough, but there has been very little research as it has not been considered to be an important area by the pharmaceutical companies."
Professor Barnes said there was evidence to suggest that many cases of chronic cough were caused by increased sensitivity of the nerve endings in the airways.