Everything you ever wanted to know about coughs (but were too bust spluttering to ask)

Will it clear up by itself? Could it be asthma or even lung cancer? And when should you see the GP?

Coughing is generally a good thing: it is a reflex action that keeps the airways clear of mucus, dust, smoke and bugs - and most coughs clear up by themselves with in three weeks. But if a cough lasts longer than this and is getting gradually worse, it is worth seeing a GP. Breathlessness, coughing up blood, unexplained weight loss, persistent hoarseness or lumps in the neck are all warning signs that need urgent medical attention.

The commonest cause

In adults, the most common cause of a longstanding cough is upper airway cough syndrome, which used to be called postnasal drip. Some people are unusually sensitive to the discharge that drips back from the nose into the throat. There is no certain way of making the diagnosis, but if treatment with a daily oral antihistamine and a decongestant work within two weeks, then you have the answer. Both are available over the counter and can be used to control the symptoms. The caveat is that it is important to see a doctor if you have additional worrying symptoms or are unsure of the diagnosis. If there is an obvious trigger, such as dust, try to avoid it - though that is easier said then done. Never use nasal decongestant for long periods as they can exacerbate the problem.

Do I have asthma? 

Sonia Munde of Asthma UK says: "Common signs of asthma include coughing, wheezing, tightness in the chest and shortness of breath. If you have a persistent cough that particularly bothers you at night and disrupts your sleep, you should see your GP."

In some people, a cough may be the only sign of asthma. Most will be helped by a blue inhaler (containing the drug salbutamol), which relieves symptoms by opening up narrowed airways, and a brown inhaler (contaning beclomethasone), which prevents symptoms by reducing inflammation in airways. Combination inhalers are also prescribed.

Some people have a cough that sounds like asthma but isn't. It is called nonasthmatic eosinophilic bronchitis and is associated with lots of cells found in allergic reactions in the airways. It doesn't improve with reliever inhalers, but preventer inhalers may work well.

Coughs can also be caused by other lung conditions, such as chronic bronchitis, which is defined as a "productive" cough that lasts more than three months over at least two years, and tends to affect smokers, and bronchiectasis, a relatively rare lung condition causing cough, breathlessness and lots of phlegm. The airways become abnormally wide and prone to repeated infections.

Reflux from the stomach

In gastro-oesophageal reflux diease, acid washes up the oesophagus from the stomach causing heartburn, difficulty swallowing, a bitter taste - and a cough. The cough may be worse on talking, getting out of bed or after eating.

Losing weight, avoiding trigger foods and taking medication that neutralizes or suppresses acid (such as Gaviscon, ranitidine or omeprazole) may help. But Professor Alyn Morice, head of cardiovascular and respiratory studies at the University of Hull, says taht a longstanding cough is often caused by non-acid gases that rise up from the stomach - and because they are not acid, the standard anti-acid treatments don't work. "The underlying problems in cough hypersensitivity syndrome (CHS) is non-acid reflux. We all produce a gaseous mist that can reflux up the oesophagus from the stomach, irritating nerves in the throat and making us cough. Temperature changes, smoke, fumes and chillis can also irritate the receptors in these nerves."

Morice estimates that up to one in 10 people may be affected by CHS. "Treatments include drugs such as metoclopramide, domperidone and baclofen, the antibiotic azithromycin or cough suppressants such as low-dose morphine."

Could it be lung cancer?

"There may be reasons to do this differently depending on the individual, but if someone has had a cough for more than four to six weeks, I would get a chest x-ray" says Professor Peter Shields, of Ohio State University. "But a negative chest x_ray is not good enough, and if the cough persists, a CT scan is needed. This may be changed if, for example, someone has some infectious symptoms. But, in all cases, a persistent cough ultimately needs imaging."

Non-smokers get lung cancer too, but 86% of cases are caused by smoking, and a small proportion are attributed to passive smoking. The number of years you smoke for is even more important than the number of cigarettes you smoke, so those who start young are at particular risk.

Could my medication cause it?

Possibly. ACE inhibitors (ramipril, lisinopril) are a group of drugs commonly prescribed to treat high blood pressure, and between 5%and 35% of users get a tickling sensation in the throat that can cause a dry cough. Onset can be days or months after starting the drug and gets better within three months of stopping it. Women, non-smokers and people of Chinese origin are more likely to develop this annoying side-effect. There is a good substitute group of drugs (including losartan) that don't cause coughing but are more expensive.

Cough medicines for children? 

At this time of year, many children roll from one viral infection to the next. Hearing your child cough all night can be worring. But Malcolm Brodlie, consultant paediatric respiratory physician at Newcastle University and the Great North Children's Hospital, says: "The probability of a serious underlying disease in a well child who is gaining weight and has an occasional cough is very small." Serious underlying diseases such as cystic fibrosis result in a child that doesn't gain weight or thrive. And Brodlie points out that since 2007 the vast majority of children with cystic fibrosis in the UK will be identified by the newborn screening programme. "A cough after a viral infection may last up to eight weeks," he says. And if you're tempted to dose them up on cough medicines, don't. "There is no role for cough medicines in children, and in young children under six, they may have adverse effects," says Brodlie.