A cough is termed "chronic", which means persisting, if it has hung around for more than eight weeks. A shorter-term cough, lasting up to three weeks, is called "acute", and if it is somewhere in the middle, it's called "subacute". Infections (such as the common cold or a chest infection) are the most common reason for acute coughs, but these usually settle within about three weeks.
What are the most common causes of chronic cough?
There are many possible causes of cough but the following are the most common.
Cigarette smoke is irritant to the lining of the airways, so being a smoker, or being around other people smoking (being a passive smoker) is a common cause of cough. Smoking-related coughs are usually dry - in other words you don't cough anything up - and tend to be worst in the mornings.
A group of medicines called angiotensin-converting enzyme (ACE) inhibitors commonly cause a cough. Examples of commonly used ACE inhibitors are lisinopril, ramipril, trandolapril and perindopril. If these medicines cause a cough, they can usually be replaced with other treatments. Some other medicines can also occasionally cause a cough. Cough caused by ACE inhibitors also tends to be a dry cough.
Catarrh coming from the back of your nose
Any condition which gives you more gunk in your nose may result in that gunk dripping down the back of your throat and making you cough. Examples of conditions which could do this are allergies, persistent rhinitis and nasal polyps. This is called postnasal drip or upper airway cough syndrome. It tends to be worse in the morning and then improve during the day, and you usually cough up some mucus, which has originally come from your nose.
Often if you have acid reflux, you are aware of it and get a burning sensation in your gullet, called heartburn. However, sometimes a cough is the only symptom of acid coming back (refluxing) up from your stomach. The stomach acid irritates the upper part of the airway around the voice box (larynx) and causes a cough. This kind of cough is sometimes worse after eating, or whilst you are eating. It may also be worse when you bend over, or while you are lying flat in bed.
Usually the cough of asthma comes with other symptoms, such as being out of breath when you exercise, or having wheezy breathing. Asthma can start with just a cough, however. The cough tends to be worse during the night, or when you exercise.
Chronic obstructive pulmonary disease (COPD)
The cough of COPD usually comes with gradually worsening breathlessness when you do anything. Colds often progress to coughs which turn into chest infections and linger. It is usually caused by many years of smoking.
Could it be cancer?
You and your doctor will always want to rule out cancer if you have a cough which lingers. Lung cancer is more likely if you have been a smoker, but can occur in anyone. Signs that it might be cancer include losing weight and coughing up blood. You may also have pain in your chest or shoulder. Lung cancer is not one of the most common causes of persisting cough, but it is definitely one to check out.
Other types of cancer in the lungs can also cause cough, such as:
- A spread of cancer from a cancer elsewhere (secondary tumours or metastases).
- Lymphoma - a cancer of the bloodstream.
What are the less common causes of chronic cough?
Other possible causes include:
- Tuberculosis (TB). This is still very common in some parts of the world, although not seen very often in the UK.
- Bronchiectasis. Usually if you have this condition, you bring up a lot of phlegm when you cough.
- Having something (a "foreign body") stuck in the airways.
- Whooping cough (pertussis). This cough tends to linger for a long time, although it has usually gone by eight weeks. There are characteristic bouts of coughing, followed by a "whoop" as you catch your breath.
- Heart failure. This means your heart isn't pumping as efficiently as it should do. Usually symptoms are being short of breath, tired and having swollen ankles. Occasionally there can be a cough.
- Interstitial lung disease. This is a scarring of lung tissue, which causes cough and breathlessness.
For more information on these conditions, follow the links where available.
Will the cause always be found?
Nope, sorry, not always. All the above conditions can be ruled out in some cases, but still leaving the cough behind. Sometimes you can be left with an unexplained cough. There are various names for this, including:
- Idiopathic cough. (Idiopathic means there is no cause to be found.)
- Chronic refractory cough.
- Cough hypersensitivity syndrome.
- Neurogenic or psychogenic cough.
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Do I need to see a doctor?
If you have had a cough which is not settling after three weeks then always see your doctor. Particularly see your doctor if you have a cough along with:
- Weight loss
- Chest pain
- Breathing problems
What will the doctor do?
When you have a lingering cough and go to see a doctor, first they will want to ask you some questions (take a history). These might include:
- Do you smoke?
- Does anyone in your family have any chest-related conditions?
- Have you ever had asthma or hay fever?
- Do you get heartburn?
- Is your nose congested or runny?
- Have you travelled abroad recently?
- Questions about the cough: How long have you had it? When did it start? Did it start after an infection? Do you bring up any phlegm or blood when you cough?
- Do you have any other symptoms? (Such as weight loss, being short of breath, night sweats or pains in your chest or shoulder.)
- What is/was your job?
- Are you on any medication?
The doctor will then want to examine you. What is checked may depend on your answers to the questions above. Examination might include:
- Looking in your throat and nose.
- Listening to your chest.
- Feeling your neck and upper chest for lymph nodes.
- Looking at your fingernail shape (this can indicate certain lung conditions).
- Checking your temperature.
- Feeling your tummy.
- Checking your ankles for swelling.
The doctors may then do some further tests in the surgery, including:
- Checking your oxygen levels. This is done with a pulse oximeter, which attaches to your finger and measures your pulse and oxygen levels.
- Checking your peak flow. You will be asked to blow into a tube (a peak flow meter) to see how well your lungs work.
- Spirometry. This is a more complex test of your lung function and you would be asked to come back to have this done in another appointment.
Will I need any tests?
Other than the tests described above, you may need further tests, depending on what has been found so far. You will almost certainly have a chest X-ray. If you produce any phlegm when you cough this will be sent off for analysis to see if it contains any germs, indicating infection. Some blood tests may be helpful.
If any of these tests show abnormalities in your lungs, you may be referred to a specialist for further investigations. These might include:
- A CT scan
- A bronchoscopy. A camera is passed with a tube into your airways, so that they can be seen and samples from the inside can be taken.
Other tests may be suggested if reflux or a nasal/sinus problem is suspected, and your cough doesn't clear up on treatment. For example, this might include an endoscopy. If a heart problem is suspected, further heart investigations such as an echocardiogram may be advised.
How can I get rid of my cough?
This will depend on the cause. Smoking irritates the airways and is one of the biggest causes of cough. If it isn't causing the cough, it certainly won't be helping it. So if you smoke, please consider quitting.
Other than that, the treatment will be specific to the cause. For example, inhalers may be prescribed for asthma, antacid medicines may be prescribed for reflux, nasal sprays may be prescribed for catarrh coming from the nose.
How will my cough be treated?
This will entirely depend on the cause. It is important to try to work this out first, in order to get you on the right treatment. For example, if it turns out to be an infection, such as TB, you would be put on a special antibiotic regime. If it turns out to be asthma or COPD, you will be given inhalers, and these adjusted until the cough improves. If you have reflux, you might be given anti-reflux medicines such as proton pump inhibitors (PPIs) or ranitidine. If you have congestion in your nose, you may be given a steroid nasal spray. Or you may be referred to an ear, nose and throat (ENT) specialist for further examination of the inside of your nose and sinuses. If you are on a medicine which has caused the cough, this can be stopped.
If you smoke, you will be advised strongly to stop smoking.
What will the treatment be if no cause is found?
This is more difficult but there are a number of options which may be tried. These include:
- Soothing preparations. These don't cure the cough but may help to soothe it a little. Examples include simple linctus and cough sweets available from pharmacies.
- Cough suppressing treatments. There are no magical treatments for suppressing cough but there are some which might be helpful, such as pholcodine or codeine.
- Medicines which may make it easier to cough up the phlegm. These medicines are called mucolytics. These are only useful in people who have coughs which are not dry.
- Steroid inhalers. These are usually used for people with asthma or COPD, but sometimes help reduce inflammation in the airways and improve a cough. They often help if your airways have persisting irritation after an infection which has settled.
- Medicines which work to make the nerves less sensitive. These include amitriptyline, gabapentin and pregabalin.
- Speech therapy.
Further reading and references
Cough; NICE CKS, June 2015 (UK access only)
Barraclough K; Chronic cough in adults. BMJ. 2009 Apr 24338:b1218. doi: 10.1136/bmj.b1218.
Johnstone KJ, Chang AB, Fong KM, et al; Inhaled corticosteroids for subacute and chronic cough in adults. Cochrane Database Syst Rev. 2013 Mar 28(3):CD009305. doi: 10.1002/14651858.CD009305.pub2.
Gibson PG, Vertigan AE; Management of chronic refractory cough. BMJ. 2015 Dec 14351:h5590. doi: 10.1136/bmj.h5590.
Faruqi S, Murdoch RD, Allum F, et al; On the definition of chronic cough and current treatment pathways: an international qualitative study. Cough. 2014 May 2910:5. doi: 10.1186/1745-9974-10-5. eCollection 2014.