What is a cough?
Note: A cough can be a symptom of coronavirus (COVID-19). Read more about coronavirus or use our Coronavirus Risk Assessment to check your risk.
A cough is a reflex action to clear your airways of mucus and irritants such as dust or smoke. It's rarely a sign of anything serious.
A "dry cough" means it's tickly and doesn't produce any phlegm (thick mucus). A "chesty cough" means phlegm is produced to help clear your airways.
Most coughs clear up within three weeks and don't require any treatment. For more persistent coughs, it's a good idea to see your doctor so they can investigate the cause.
What can cause a cough?
Some of the main causes of short-term (acute) and persistent (chronic) coughs are outlined below.
Short-term coughs
Common causes of a short-term cough include:
- an upper respiratory tract infection (URTI) that affects the throat, windpipe or sinuses – examples are a cold, flu, laryngitis, sinusitis or whooping cough
- a lower respiratory tract infection (LRTI) that affects your lungs or lower airways – examples are acute bronchitis or pneumonia
- an allergy, such as allergic rhinitis or hay fever
- a flare-up of a long-term condition such as asthma, chronic obstructive pulmonary disease (COPD) or chronic bronchitis
- inhaled dust or smoke
In rare cases, a short-term cough may be the first sign of a health condition that causes a persistent cough.
Persistent coughs
A persistent cough may be caused by:
- a long-term respiratory tract infection, such as chronic bronchitis
- asthma – this also usually causes other symptoms, such as wheezing, chest tightness and shortness of breath
- an allergy
- smoking – a smoker's cough can also be a symptom of COPD
- bronchiectasis – where the airways of the lungs become abnormally widened
- postnasal drip – mucus dripping down the throat from the back of the nose, caused by a condition such as rhinitis or sinusitis
- gastro-oesophageal reflux disease (GORD) – where the throat becomes irritated by leaking stomach acid
- a prescribed medicine, such as an angiotensin-converting enzyme inhibitor (ACE inhibitor), which is used to treat high blood pressure and cardiovascular disease
Rarely, a persistent cough can be a symptom of a more serious condition, such as lung cancer, heart failure, a pulmonary embolism (blood clot on the lung) or tuberculosis.
Coughs in children
Coughs in children often have similar causes to those mentioned above. For example, respiratory tract infections, asthma and GORD can all affect children.
Causes of coughs that are more common in children than adults include:
- bronchiolitis – a mild respiratory tract infection that usually causes cold-like symptoms
- croup – this causes a distinctive barking cough and a harsh sound known as stridor when the child breathes in
- whooping cough – look out for symptoms such as intense, hacking bouts of coughing, vomiting, and a "whoop" sound with each sharp intake of breath after coughing
Occasionally, a persistent cough in a child can be a sign of a serious long-term condition, such as cystic fibrosis.
When to see your doctor
There's usually no need to see your doctor if you or your child have a mild cough for a week or two. However, you should seek medical advice if:
- you've had a cough for more than three weeks
- your cough is particularly severe or is getting worse
- you cough up blood or experience shortness of breath , breathing difficulties or chest pain
- you have any other worrying symptoms, such as unexplained weight loss, a persistent change in your voice, or lumps or swellings in your neck
If your doctor is unsure what's causing your cough, they may refer you to a hospital specialist for an assessment. They may also request some tests, such as a chest X-ray, allergy tests, breathing tests, and an analysis of a sample of your phlegm to check for infection.
What treatments are available?
Treatment isn't always necessary for mild, short-term coughs because it's likely to be a viral infection that will get better on its own within a few weeks. You can look after yourself at home by resting, drinking plenty of fluids, and taking painkillers such as paracetamol or ibuprofen.
Cough medicines and remedies
Although some people find them helpful, medicines that claim to suppress your cough or stop you bringing up phlegm are not usually recommended. This is because there's little evidence to suggest they're any more effective than simple home remedies, and they're not suitable for everyone.
The Medicines and Healthcare products Regulatory Agency (MHRA) recommends that over-the-counter cough and cold medicines shouldn't be given to children under the age of six. Children aged 6 to 12 should only use them on the advice of a doctor or pharmacist.
A homemade remedy containing honey and lemon is likely to be just as useful and safer to take. Honey shouldn't be given to babies under the age of one because of the risk of infant botulism .
Treating the underlying cause
If your cough has a specific cause, treating this may help. For example:
- asthma can be treated with inhaled steroids to reduce inflammation in your airways
- allergies can be treated by avoiding things you're allergic to and taking antihistamines to dampen down your allergic reactions
- bacterial infections can be treated with antibiotics
- GORD can be treated with antacids to neutralise your stomach acid and medication to reduce the amount of acid your stomach produces
- COPD can be treated with bronchodilators to widen your airways
If you smoke, quitting is also likely to help improve your cough.
Causes of a cough
Most coughs are caused by viral infections and usually clear up on their own.
Short-term cough (acute)
Most people with a cough have a respiratory tract infection caused by a virus. This includes:
- upper respiratory tract infections (URTIs), which affect the throat, windpipe or sinuses - such as the common cold, influenza (flu), laryngitis, sinusitis or whooping cough
- lower respiratory tract infections (LRTIs), which affect your lungs or lower airways - such as acute bronchitis and pneumonia (although this is rare)
Possible non-infectious causes of an acute cough include:
- allergic rhinitis, such as hay fever
- a flare-up of a chronic condition such as asthma, chronic obstructive pulmonary disease (COPD) or chronic bronchitis
In rare cases it may be the first sign of a health condition causing a chronic (long-term) cough (see below).
Long-term cough (chronic)
A persistent cough in adults may be caused by:
- a long-term respiratory tract infection
- a long-term condition, such as asthma
- allergies
- smoking - smoker's cough can also be a symptom of chronic obstructive pulmonary disease (COPD)
- postnasal drip (mucus dripping down the throat from the back of the nose, caused by a condition such as rhinitis)
- gastro-oesophageal reflux disease - due to irritation and damage caused by stomach acid
- a prescribed medicine, such as an angiotensin-converting enzyme (ACE)-inhibitor, used to treat high blood pressure or cardiovascular disease
Rarely, a cough is a symptom of a more serious condition such as lung cancer, heart failure, a pulmonary embolism (clot on the lung), cystic fibrosis or tuberculosis (TB).
Coughs are usually classified by doctors according to how long they last:
- a cough that lasts for less than three weeks is described as an acute cough
- a cough that gets better over a three-to-eight-week period is described as a subacute cough
- a cough that lasts for longer than eight weeks is known as a chronic (persistent) cough
Treatment for a cough
There's no quick way of getting rid of a cough that's caused by a viral infection. It will usually clear up after your immune system has fought off the virus.
If there is an underlying condition causing a cough, this will need specific treatment.
The simplest and cheapest way to treat a short-term cough may be a homemade cough remedy containing honey and lemon. The honey is a demulcent, which means it coats the throat and relieves the irritation that causes coughing.
Cough medicines
There's little evidence to suggest cough medicines actually work, although some ingredients may help treat symptoms associated with a cough, such as a blocked nose or fever.
Some contain paracetamol, so don't take more than the recommended dosage. Cough medicines should never be taken for more than two weeks.
They can be used for any type of cough and are generally safe, but diabetics should note that they're usually sugar-based.
Treating children
The Medicines and Healthcare products Regulatory Agency (MHRA) has recommended that over-the-counter cough and cold medicines shouldn't be given to children under the age of six.
The MHRA is the government body responsible for ensuring medicines are safe and effective.
The agency has made this recommendation because it feels there's a potential risk of these medicines causing unpleasant side effects, such as allergic reactions, sleep problems or hallucinations (seeing and hearing things that aren't real). These would outweigh any benefit provided by the medicines.
Instead, give your child a warm drink of lemon and honey or a simple cough syrup that contains glycerol or honey. However, honey shouldn't be given to babies under the age of one, due to the risk of infant botulism.
Cough suppressants
Cough suppressants, such as pholcodine, dextromethorphan and antihistamines, act on the brain to hold back the cough reflex. They're used for dry coughs only.
- Pholcodine have few side effects or interactions with other medicines.
- Antihistamines sometimes cause drowsiness, which can be helpful if your cough is disrupting your sleep. Other possible side effects are a dry mouth, constipation, difficulty in passing urine and blurred vision. Antihistamines might interact with other medicines, such as antidepressants and those that cause drowsiness.
Check with your doctor or pharmacist before taking cough suppressants.
Expectorants
Expectorants help bring phlegm up so that coughing is easier, which may help chesty coughs. They include:
- guaifenesin
- ammonium chloride
- squill
- sodium citrate
- ipecacuanha
These compounds are all found in small quantities in cough mixtures, so they're unlikely to have any side effects or interact with other medicines.
Quitting smoking
If you have a cough caused by smoking you'll quickly start to notice the benefits of quitting. Three to nine months after you stop smoking, your breathing will have improved, and you will no longer have a cough or wheeze.
Giving up smoking also increases your chances of living a longer and healthier life. Other health benefits include:
- after one month your skin will be clearer, brighter and more hydrated
- after one year your risk of heart attack and heart disease will have fallen to about half that of a smoker
