A cough is a reflex action to clear your airways of mucus and irritants such as dust or smoke.
Coughs may be dry or chesty (see below) and most coughs clear up within three weeks.
Treatment isn't usually necessary, but a home remedy containing honey and lemon may help ease a short-term cough.
There's little evidence to suggest that cough medicines will be any more effective.
Dry or chesty cough?
Dry coughs are usually felt in the throat as a tickle that sets off the coughing.
It happens when the throat and upper airways become inflamed (swollen). No phlegm (thick mucus) is produced.
The common cold or flu causes a dry cough because your brain thinks the inflammation in your throat and upper airways is a foreign object and tries to remove it by coughing.
A chesty cough usually produces phlegm. The cough is helpful, because it clears the phlegm from your lung passages.
When to see your GP
See your GP if you've had a cough for more than three weeks after a viral infection, or if your cough is progressively getting worse.
If you experience breathing difficulties, chest pain or you cough up blood, speak to your GP immediately.
If your GP is unsure what's causing your cough they may refer you to a respiratory specialist. They may also request some tests, including:
a chest X-ray - to see if you have a chest infection
taking a sample of your phlegm for analysis - to help decide if antibiotics should be prescribed
spirometry (breathing in and out of a tube connected to a machine) - to see if you have an underlying respiratory condition
allergy testing - to see whether your cough is caused by something you're allergic to, such as house dust mites
What causes a cough?
Most people with a cough have a respiratory tract infection caused by a virus. Possible non-infectious causes include:
allergic rhinitis, such as hay fever
a flare-up of a long-term condition such as asthma, chronic obstructive pulmonary disease (COPD) or chronic bronchitis
gastro-oesophageal reflux disease - due to irritation and damage caused by stomach acid
In rare cases it may be the first sign of a condition causing a long-term cough.
Watch as a GP describes the most common causes for coughs and how they can be treated.
Cough in children
If your child has a bad cough that won't go away, see your GP. A persistent cough may be a sign of a more serious respiratory tract infection.
It is also important to be aware of the symptoms of whooping cough, especially in young children and babies.
Symptoms of whooping cough include:
intense, hacking bouts of coughing, which bring up thick phlegm
a 'whoop' sound with each sharp intake of breath after coughing
vomiting in infants and young children
fatigue and redness in the face from the effort of coughing
Causes of a cough
Most coughs are caused by viral infections and usually clear up on their own.
Doctors often classify coughs according to how long they last. For example, a cough is classed as:
acute - if it lasts for less than three weeks
subacute - if itlasts for 3-8 weeks
chronic (persistent) -if it lasts for more than eight weeks
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
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 (GORD) - due to irritation and damage caused by stomach acid
a prescribed medicine, such as an angiotensin-converting enzyme inhibitor (ACE inhibitor), that's used to treat high blood pressure (hypertension) 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).
Treating a cough
There's no quick way of getting rid of a cough 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.
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.
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, such as pholcodine, dextromethorphan and antihistamines, act on the brain to hold back the cough reflex. They're used for dry coughs only.
Pholcodine and dextromethorphan 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 GP or pharmacist before taking cough suppressants.
Expectorants help bring phlegm up so that coughing is easier, which may help chesty coughs. They include:
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.
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
Antibiotics are not used to treat coughs because they are only effective in killing bacteria, not viruses.
Therefore, unless you develop a secondary bacterial infection, such as pneumonia, antibiotics will not usually be advised.