When should you worry about a persistent cough?
Coughing is common during the winter colds and flu season – but what if it carries on past a few weeks? Our expert guide explains when to get it checked by a doctor.
Coughing is common during the winter colds and flu season – but what if it carries on past a few weeks? Our expert guide explains when to get it checked by a doctor.
Whether coughs are tickly, hacking, dry, or chesty ones that bring up phlegm, they can have a big impact – disrupting sleep at night, causing social embarrassment, exacerbating incontinence and spreading infection. But when do they become something to worry about?
Persistent coughs lasting more than eight weeks affect an estimated five to 10 per cent of the UK’s adult population, according to some estimates.
“Coughs are one of the most common medical complaints that patients see a doctor for,” says Professor James Hull, a consultant respiratory medicine specialist at HCA’s The Princess Grace Hospital, and clinical lead for chronic coughs at the Royal Brompton Hospital, both in London.
“While most are short-term, some can be more persistent, lasting many weeks or even months. In those cases, you should seek medical help for imaging to find out if there is a more serious underlying cause.”
“The first thing to say is that most causes of persistent cough are nothing to be frightened of – at this time of year, it’s mostly either an active viral infection or an irritated, damaged lining of your airways,” says Tom Routledge, consultant thoracic surgeon and lung cancer specialist at HCA London Bridge Hospital and Guy’s and St Thomas’ Hospital, both in London.
“That means your cough persists for much longer than the acute infectious illness itself. So, you might have flu for a week or two, but it's not unusual for a cough to persist for two or three weeks after that when your airways are healing.”
Coughing is a protective reflex that protects the lungs from foreign bodies and helps us clear mucus.
It’s triggered when nerve receptors that line the respiratory tract sense irritants, and then expel air and particles out of the lungs and throat to clear them.
“The nerve fibres in the respiratory tract send a message up to the cough control centre in the brain, and that relays a message back that causes the closure of the airways,” explains Professor Hull.
“The nerve circuit detects things that are perceived as either structurally, physically or chemically potentially harmful to the lungs.”
“Studies have shown that the majority of cough medicines are no better than placebo,” says Professor Hull.
“It’s important to be well hydrated, rest and give the cough time to clear – most will resolve within seven to 10 days. Some people find that using manuka honey, cloves in a hot drink, and/or lozenges with menthol may also be beneficial.”
Other treatments for coughs will depend on the underlying causes. For example, a bacterial chest infection can be treated with antibiotics; a cough caused by acid reflux can be treated with drug treatments such as proton pump inhibitors to stop stomach acid production; and asthma can be controlled with inhalers and inhaled steroids.
“An estimated 1–2.5% of people over the age of 50 develop a cough that is either persistent or recurrent, and that doesn’t seem to respond to treatments, and we think this is caused by a condition we now call cough hypersensitivity syndrome,” says Professor Hull.
“This is also known as a neuronal cough or a nerve hypersensitivity cough. But that’s not to say the coughing is due to someone being nervous – it’s to do with the fact that their nerve fibres are sensitised. It’s quite a substantial problem.”
However, Professor Hull says that, in some people, coughs can be triggered by anxiety and stressful situations such as public speaking, making presentations or being in the audience at the theatre.
“If people are nervous or anxious, the body automatically heightens its protective reflexes," he explains. "Some people can have nerve hypersensitivity and coughs triggered by stress and anxiety at the same time,” he says.
“These people can feel excluded socially because they know they will cough in certain social scenarios, such as at the cinema or when meeting groups of people, and people will move away from them or exclude them – it’s an awful thing to have.”
The first drug for hypersensitivity coughs, called Gefapixant (Lyfnua), was approved by the UK’s Medicines and Healthcare Products Regulatory Agency (MHRA) in 2023, but has not yet been approved for NHS use by the National Institute for Health and Care Excellence (NICE), and is only available privately.
It works by blocking receptors on sensory nerves that are overactive in cough hypersensitivity, and reduces coughs by 60% in some patients, according to a King’s College Hospital study.
A persistent cough is defined as one that lasts more than eight weeks, says Professor Hull.
“If you have a cough that continues for longer than four to six weeks, it's important to get it checked with medical imaging, such as a chest X-ray or a CT scan, to rule out any serious underlying conditions.
“This evaluation should also include reviewing your medications to see if they might be causing the cough. By considering additional symptoms, doctors can help determine whether issues like postnasal drip, allergies or acid reflux are contributing factors.”
Seek medical help if you experience any of the following:
“The key thing is persistence – if you have a cough above four to six weeks, you need imaging, even if you don’t have any of the red flags above,” stresses Professor Hull. “I’ve seen lung cancer cases in people who only had a mild, dry cough – you don’t necessarily cough up blood.”
Routledge says that your doctor would also consider other concerning symptoms, such as your breathing being less good, and you being more short of breath during and after exercising.
“These could be signs of more serious illnesses, not just lung cancer,” he explains. “If you cough up any blood even during the acute phase of an infection, that should warrant a trip to the doctor for checking.
“In the longer term, if you look back and you haven’t been feeling well for months, and/or you’ve been losing weight unintentionally over the last few months accompanying your cough, that will always warrant more investigation.”
Routledge says that smokers (even those who quit decades ago) should have a lower threshold for seeking help with the above symptoms, as they are at higher risk.
These include a number of diseases that your doctor will want to rule out or diagnose at an early stage.
“The obvious worry is lung cancer,” says Routledge.
“People tend to wait until they have symptoms to get checked out, and in lung cancer you don’t get symptoms (such as breathlessness and coughing) until a late stage. It is often diagnosed in A and E with very severe symptoms.”
He says that although newer drugs such as immunosuppressants have greatly improved treatments for lung cancer, these are most effective if it is diagnosed at an early stage. Five-year survival with stage 1 lung cancer is 90% compared to 4% at stage 4.
Lung cancer is still the leading cause of cancer deaths in the UK, with 33,100 people dying each year, according to Cancer Research UK.
A national lung cancer screening programme is now being rolled out across England, and also planned for Wales, identifying people aged 55 to 74 who are smokers or who have ever smoked for a lung health check, including a CT screening scan if judged necessary. In 2024, it was reported to have picked up more than 5,000 lung cancers, 76% at an early stage (60% at stage 1).
The University of Aberdeen is evaluating a blood test combined with imaging to see if it can reduce late-stage lung cancer diagnosis.
“In the winter months particularly, a viral infection can lead to a secondary lung infection such as pneumonia or bacterial bronchitis (inflammation of the lungs usually caused by an infection), which may need a course of antibiotics,” says Routledge.
Also known as pulmonary fibrosis, this is scarring of the lung tissue, which makes it stiffer and harder to breathe. Symptoms include shortness of breath, a dry cough and extreme fatigue.
This is a long-term lung condition where the lungs become inflamed and damaged, making breathing more difficult. It’s usually caused by breathing in harmful chemicals such as cigarette smoke and fumes.
A persistent cough is one of the symptoms, as is coughing up phlegm and breathlessness. Treatments include using bronchodilators and steroids, but giving up smoking is the most important first step.
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