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When to worry about a persistent cough

While we think of coughs as troublesome, they're actually your body's way of protecting your airways, getting rid of foreign bodies including germs. Coughs lasting under three weeks are most commonly down to viral infections, but when should you seek medical help?


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As many as one in five of us have a persistent cough, which usually doesn't have a serious cause but can be exhausting - especially if it stops us sleeping.

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What's persistent?

Doctors describe a persistent, or 'chronic', cough as one lasting more than eight weeks. Three to eight weeks is 'sub-acute' and less than three weeks is 'acute'.

The time your cough lasts is important because chronic coughs usually have different causes (and treatments) to others. Coughs lasting less than three weeks are usually caused by viruses, and self-help remedies from your pharmacist will help you through them.

See your doctor if your cough persists for more than three weeks or you get other symptoms like shortness of breath, chest pain or coughing up blood. Likewise, if you have a long-term chest condition like asthma or COPD, you need to contact your doctor if the cough has made these symptoms worse.

What's causing your persistent cough?

When I was a student learning to examine patients, my consultant always reminded me that to examine a patient's abdomen properly, you had to check them out 'from nipples to knees'. Likewise, a cough can be caused by irritation of the airways anywhere from your throat to the bottom of your lungs. Some are obvious, but you might be surprised at the culprits your GP will point the finger at.


If you smoke or have smoked, chronic cough could be due to a chronic lung condition called COPD (sometimes called emphysema or chronic bronchitis). If you're over 35, have ever smoked and have chronic cough, bring up sputum regularly, get bronchitis in winter, and get wheezy or out of breath, COPD may be to blame. It can be diagnosed easily by a test called spirometry, which involves blowing into a special machine.


Asthma usually comes on in childhood but can start later in life. Both can be treated with inhalers, but stopping smoking is still essential. If you don't smoke but work in a smoky atmosphere or with chemicals or fumes, they can irritate your upper airways, causing persistent tickly cough.

Postnasal drip

Colds, allergies and chronic sinusitis can cause a drip down the back of your throat which irritates your upper airways, especially when you lie down. Do you suffer from a permanently blocked nose and a nasty taste in the back of your throat?

Treatments for sinusitis vary depending on how long you've had it, how severe your symptoms are and whether you have polyps in your sinuses.

Allergies like hay fever and persistent rhinitis (constantly blocked nose caused by allergy to house dust, meaning symptoms are often worse in winter and when you're indoors) can be treated with nasal sprays and antihistamine tablets.

Acid reflux

When I talk to my patients about 'reflux', they normally think of heartburn - that burning pain behind your breastbone that's worse when you lie flat. It can also give rise to an acid taste in your mouth, and this acid can irritate the throat. It's one of the most common causes of chronic cough. Solutions include anti-acid medicine, losing weight, avoiding eating late at night, and not wearing tight belts or trousers. Propping the head of the bed up a bit (with a brick under the top legs) can also help.

Heart problems

If your heart isn't pumping blood around your system as efficiently as it should, it can lead to a 'logjam' of fluid which builds up in your lungs. This is called heart failure - although it's not strictly a 'failure' of the heart. Other pointers to heart failure include shortness of breath on exercise or lying flat; swollen ankles and waking up in the night gasping for breath. The outcome for heart failure patients has improved dramatically in recent years with the advent of new medical treatments.

Some medications

A groups of medicines used very commonly to treat high blood pressure can cause dry, irritating cough in up to one in 10 men and one in five women. They're called the ACE inhibitors and have names ending in '-pril' (enalapril, lisinopril, etc). Symptoms can start when you've taken them without problem for months or even years. Speak to your GP if you think they may be to blame - there are alternatives that don't cause cough

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Could it be cancer?

Public Health England's 2016 campaign 'Be clear on cancer' aimed to raise awareness of the risks of lung cancer and its link with persistent cough. At least once a week, I have a patient in who’s worried their cough is due to cancer. It rarely is - other causes are much more likely. However, always see a doctor if your cough lasts for more than three weeks, or is accompanied by coughing up of blood or rusty-coloured sputum; wheeziness or difficulty in breathing; or sharp stabbing chest pain when you breathe (rather than when you cough).

The National Institute for Health and Care Excellence (NICE) has guidelines on when cancer should be suspected. They recommend you should have a chest X-ray within two weeks if you're over 40 and have two symptoms out of cough, shortness of breath, tiredness, chest pain, weight loss or loss of appetite.

If you're over 40 and have ever smoked, just one of these symptoms should trigger a referral for chest X-ray. However, be aware that the proviso is that the symptoms should be unexplained - so having a cough for a week or two accompanied by other symptoms of infection with a virus (runny nose, fever, etc) doesn't raise the same alarm bells.

Trust your pharmacist

Most coughs that accompany a cold will settle in one to two weeks. It's not uncommon to be infected with more than one virus at the same time, so symptoms may overlap and last longer from start to finish. They're almost all caused by viruses, so antibiotics don't do any good at all. In fact, we can't 'cure' them, but there are a lot of things that you can do to help relieve the symptoms.

Your pharmacist is the expert here - they can advise you on all sorts of remedies, depending on what combination of symptoms you have. For instance, with a chesty cough you bring up yellow or green phlegm or mucus, while a dry, tickly cough usually doesn't come with any sputum.

You'll get best results from cough mixtures designed for the kind of cough you have. You may also find that your cough gets worse at night - this is because when you're upright during the day, the mucus from your nose trickles down the back of your throat and you swallow it. At night when you're lying down, it trickles on to your soft palate and stimulates your cough reflex. If you're kept awake by coughing when you lie flat, make a nest of pillows so you're propped up.

Being cold for long periods may increase the chance of illnesses like chest infections - so don't sleep with the window open! However, there's no reason to avoid going out entirely if you have a cold, as long as you're well wrapped up.

Article history

The information on this page is peer reviewed by qualified clinicians.

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