Cough

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 box, below left). They are also classified according to how long they last:

  • acute cough lasts for less than three weeks
  • subacute cough gets better over a three-to-eight-week period
  • chronic (persistent) cough lasts for longer than eight weeks

Coughs caused by the common cold or by flu usually clear up after several days. Most coughs clear up within two weeks. 

What are the causes?

Most people with a cough have a respiratory tract infection caused by a virus, such as the common cold, flu or bronchitis.

A persistent cough in adults may be caused by a condition such as rhinitis or asthma, or by a prescribed medicine such as an angiotensin-converting enzyme (ACE)-inhibitor, which treats heart disease, or by smoking.

In children, a persistent cough may indicate a more serious respiratory tract infection such as whooping cough.

When to see your doctor

If you have had a cough for more than two weeks following a viral infection, or if your cough is progressively getting worse, see your GP.

 

Inflammation
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.
Embolism
An embolism is the sudden blockage of a blood vessel, usually by a blood clot or air bubble.

Dry cough versus chesty cough

Dry cough

A dry cough happens when the throat and upper airways become inflamed (swollen). It is non-productive, which means that phlegm (thick mucus) is not 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.

Dry coughs are usually felt in the throat as a tickle that sets off the coughing.

Chesty cough

A chesty cough usually produces phlegm. The cough is helpful, because it clears the phlegm from your lung passages.

Most coughs are caused by viral infections and usually clear up on their own.

Acute cough

Most people with an acute cough have a respiratory tract infection caused by a virus.

It will usually be an upper respiratory tract infection (URTI), which means the virus has affected your throat or windpipe. Examples of URTIs causing cough are:

If your cough is caused by a lower respiratory tract infection (LRTI), the virus has infected your airways lower down or your lungs. Examples of LRTIs are: 

  • bronchitis
  • pneumonia (although this is rare) 

Other possible causes for an acute cough are allergic rhinitis, such as hayfever, or in rare cases it may be the first sign of a chronic disease (see below).

Chronic cough

Common causes of a persistent cough in adults are:

  • smoking
  • postnasal drip (mucus dripping down the throat from the back of the nose, caused by a condition such as rhinitis)
  • asthma
  • gastro-oesophageal reflux disease

Some prescribed medicines can also cause a persistent cough (for example, angiotensin-converting enzyme [ACE]-inhibitors, which are medicines for treating high blood pressure or heart failure).

In children, common causes are:

  • respiratory tract infections, such as bronchitis or whooping cough
  • asthma
  • gastro-oesophageal reflux 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) or tuberculosis (TB).

Glossary

Brain
The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.
Inflammation
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.
Lung
Lungs are a pair of organs in the chest that control breathing. They remove carbon dioxide from the blood and replace it with oxygen.

How long a cough lasts for depends on the cause. If it has been caused by the common cold, it can clear up after two to three days. Most coughs clear up within two weeks.

A dry cough will feel like a constant tickle in your throat. When you cough, there will not be any phlegm (thick mucus).

If you have a chesty cough as a result of a respiratory infection, you may cough up phlegm.

If you have a cough due to a viral infection, such as flu or bronchitis, you will not usually need to see a doctor unless your symptoms are severe.

When to see your doctor

See your GP if your cough has lasted for more than two weeks or is getting progressively worse.

Occasionally a secondary bacterial infection occurs, which can lead to a more serious condition developing, such as pneumonia.

Typical symptoms of pneumonia include rapid and shallow breathing, wheezing and coughing up phlegm that may be yellow, green, brownish or blood-stained.

Symptoms of whooping cough

Symptoms of whooping cough may 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

'Red flag' signs in children

The following may indicate a serious condition:

  • a cough that occurs with feeding
  • a cough that is persistent with phlegm
  • a cough that is associated with night sweats or weight loss
  • a cough that is not getting better or is getting worse

Coughs caused by the common cold or by flu usually clear up after several days, so you will not have to see your GP.

If you have had a cough for more than two weeks following a viral infection, seek medical advice from your GP.

Your GP will take your medical history and do a full clinical examination and sometimes take some tests.

Tests

Your GP may request a chest X-ray to see if you have a chest infection and, if there is an infection, to determine the extent of this.

If you have a chesty cough, a sample of your coughed-up phlegm may be taken for analysis in a laboratory, to determine which germ has caused the infection. This information can then be used to decide whether or not antibiotics should be used to treat it

Spirometry may be used to see if you have an underlying respiratory condition. It involves breathing in and out of a tube connected to a machine, so that your GP can assess whether or not your airways have narrowed.

If your GP thinks you may have asthma, you may be prescribed asthma medication for a trial period to see if this helps.

You may have allergy testing, such as a skin prick test, to see if your cough is caused by something you are allergic to, such as house dust mites.

Referral

If your GP is unsure what is causing your cough or your cough is getting worse, they may refer you to a respiratory specialist.

Glossary

X-ray
An X-ray is a painless way of producing pictures of inside the body using radiation.
Antibiotics
Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. For example amoxicillin, streptomycin and erythromycin.
Inflammation
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

If your child has inhaled something...

If you think your child is coughing because they have inhaled an object, see your GP straight away.

They may need to be referred for an urgent bronchoscopy (test that views the airways).

There is no quick way of getting rid of a cough that is caused by a viral infection. It will usually clear up after your immune system has defeated the virus.

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. If diabeteic discuss with GP.

Cough medicines

There is little evidence to suggest that cough medicines actually work, although some of the ingredients may help treat symptoms associated with a cough, such as a blocked nose or fever.

Some contain paracetamol, so be careful not to take more than the recommended paracetamol dosage especially if taking more than one type of medicine.. 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 are usually sugar based.

Treating children

The Irish Medicines Board (IMB) has recommended that over-the-counter cough and cold medicines should not be given to children who are under the age of six.

The IMB is the regulatory body responsible for ensuring that medicines are safe and effective.

The IMB made this recommendation because it feels there is a potential risk that these medicines could cause unpleasant side effects, such as allergic reactions, sleep problems or hallucinations (seeing and hearing things that are not real), outweighing any benefit provided by the medicines.

Cough suppressants

Cough suppressants, such as pholcodine, dextromethorphan and antihistamines, act on the brain to hold back the cough reflex. They are 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

Expectorants help bring phlegm up so that coughing is easier. They include:

  • guaiphenesin
  • ammonium chloride
  • squill
  • sodium citrate
  • ipecacuanha

These compounds are all found in small quantities in cough mixtures, so they are unlikely to have any side effects or interact with other medicines.

Glossary

Immune system
The immune system is the body's defence system, which helps protect it from disease, bacteria and viruses.
Bacteria
Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.
Decongestant
Decongestant medicine relieves congestion by reducing the swelling of the lining the nose and sinuses and drying up the mucous.
Fever
A high temperature, also known as a fever, is when someone's body temperature goes above the normal 37C (98.6F).
Expectorants
Expectorant medicine helps you to cough up phlegm.
Congestion
Congestion is an excess of fluid in part of the body, often causing a blockage.
Antibiotics
Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. For example amoxicillin, streptomycin and erythromycin.
Antihistamines
Antihistamine medicine counteracts the action of histamine (a chemical released during an allergic reaction). For example loratadine, hydroxyzine.
Antidepressants
Antidepressant medicine is used to treat depression. For example Fluoxetine, Paroxetine.

Antibiotics

Useful Links

Antibiotics are not used to treat uncomplicated 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.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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