Coughing is an automatic reaction to try to clear your airways. The cough reflex protects the airways of your lungs. However, it is important to seek medical attention if you have a cough that lasts for more than three weeks. If you're short of breath, cough up blood or have unexplained problems like weight loss or a high temperature (fever), you should see your GP urgently. The most common causes are mentioned below.
What is a cough?
A cough is an automatic (reflex) muscle action that forces air up and out of your lower airways (lungs) and upper airways (windpipe, nose and mouth). Everyone will cough occasionally to 'clear their throat'. The cough reflex protects the airways of your lungs. You may cough if the airways are partially blocked by mucus (when you have a cold or chest infection for example). You may cough if you choke on food and it enters your windpipe instead of going down the food pipe (oesophagus). Or you may need to cough if you breathe in chemicals or smoke that irritate your airways.
Doctors divide cough symptoms as follows:
- Acute, meaning it lasts for less than three weeks.
- Subacute, if it lasts for three to eight weeks.
- Chronic, meaning it lasts for longer than eight weeks.
Cough affects us all if we need to clear our airways. Acute cough usually improves after one week. The most common cause is a viral infection which causes a runny nose and cough. Viral infections can affect anyone. However, young children commonly have 5-6 viral infections a year, especially in the winter months. Chronic cough is common. 1-2 adults in 10 are affected.
What causes cough?
Common causes of acute cough (lasting less than three weeks)
- Upper respiratory tract infections. These are the most common cause of acute coughs. They are caused by infection with a germ (virus). They almost always get better within a week, without specific treatment. Symptoms may go on for up to three weeks.
- Lower respiratory tract infections. These are less common; they can lead to more serious lung infections such as bronchitis or pneumonia. These conditions may be caused by infection with germs (viruses, bacteria or fungi).
- Asthma. This causes wheeze, breathlessness and cough at night, in cold air and during exercise. An infection with a germ can make symptoms of asthma much worse. This is called an exacerbation of asthma.
- Irritants - smoke or chemical fumes that you breathe in may irritate the airways.
Common causes of subacute cough (lasting three to eight weeks)
- Airways that are slow to settle down after an infection. In this case the germ has gone, but your airways are still swollen and irritable, causing you to keep coughing. This is called airway hyper-responsiveness.
- Whooping cough.
- Other infections which may cause a longer-lasting cough, such as tuberculosis (TB).
Common causes of chronic cough (lasting more than eight weeks)
- Postnasal drip. This is a condition where mucus in the nose drips down the back of the throat when you lie down. It can be caused by anything which causes your nose to produce more mucus. This includes allergies, hay fever and nasal polyps as well as infections.
- Acid reflux. Acid in the stomach washes up the food pipe and spills into the airways.
- Asthma. Undiagnosed or under-treated asthma causes cough.
- Side-effects of medication. For example, angiotensin-converting enzyme (ACE) inhibitor medicines, which are used to treat high blood pressure, can cause cough.
- Lung disease caused by smoking - chronic obstructive pulmonary disease (COPD). Lung damage causes cough and breathlessness to get steadily worse. This mainly affects smokers.
- Irritants such as cigarette smoke. This may be your own cigarette smoke, or from being in contact with other people's smoke (passive smoking).
Less common causes of cough
- A foreign body. Food can go down the windpipe instead of the food pipe. Other objects may also be inhaled by accident, such as beads, particularly in children.
- Lung cancer. This is more likely in smokers.
- Cystic fibrosis. This is an inherited condition that affects the lungs and causes chronic cough.
- Pneumothorax. In this condition, air gets trapped outside the lung, inside the chest.
- Bronchiectasis. This is a condition where airways of the lungs are excessively widened and produce extra mucus.
- A blood clot in the lung (pulmonary embolus).
What investigations may be advised?
The doctor will want to know how long your cough has lasted and whether you have any other symptoms. The doctor will particularly ask about symptoms which may suggest an underlying serious condition ('red flags').
Red flag symptoms that may suggest serious underlying disease:
Your doctor will want to know:
- Did it start suddenly or develop over time? Did anything trigger it? How long has it lasted?
- When do you cough? Is it worse when you exercise?
- Are you breathless even when you're not coughing?
- Have you got any pain in your chest?
- Are you coughing up anything? What colour is it? Is there any blood?
- Do you feel ill? Do you have a high temperature (fever), weight loss or sweats?
- Have you lost weight?
- Have you been in contact with anyone with TB or travelled abroad recently?
- Do you smoke?
- What is your occupation?
- Have you started any new medication recently?
These details will help the doctor to make a diagnosis. Your doctor will examine you. He or she will check your throat, lungs and heart. You may be asked to have lung function tests including a blowing test called a peak flow reading. Another blowing test which can be done in your GP surgery is called spirometry. You may be sent for a chest X-ray. Further tests of your lungs may be necessary.
What treatments may be offered?
Treatment will depend on the likely cause of your cough.
For acute coughs due to viral infections, simple remedies may be all that is needed. This might include inhaling steam, or honey and lemon to soothe your throat. If you feel unwell with a temperature or aches and pains, paracetamol or ibuprofen may help. The cough will go away with time on its own.
You will be strongly encouraged to stop smoking if you are a smoker. You will be offered inhalers if you have asthma. If the cough is due to tablets given for high blood pressure, you can switch to another type. If bacterial infection is likely, you may be prescribed antibiotics. A steroid nasal spray may help postnasal drip. Losing weight, cutting out acid foods and alcohol and taking medicine to stop acid in the stomach may all help acid reflux.
You may be referred to a lung (respiratory) specialist for further tests. Most cases will be managed by your GP but you may be referred for further investigation and treatment at a hospital.
What should I do if I develop a cough?
This will depend on how long the cough has lasted and how unwell you are feeling. If you feel well and the cough has not lasted long, you may not need to do anything but wait for it to settle. Simple remedies as described above may help while you wait for it to go on its own. See your GP if your cough lasts more than three weeks and is not improving. See your GP urgently if you feel very unwell, or if you develop red flag symptoms (see above). Use your reliever inhaler as instructed if you have asthma.
You should call an ambulance (999/112/911) if you experience unexpected and severe cough and difficulty in breathing that lasts for more than a few minutes. Otherwise, you should call your GP if concerned.
How can I avoid coughing?
You will need to find the underlying cause and try to address it if possible. Don't smoke, or get help to stop smoking, because all common serious causes of chronic cough are more likely to affect smokers. Try to avoid dusty or smoky places. Use your asthma medication as advised. Avoid over-the-counter cough medicines. You can take paracetamol or ibuprofen for high temperature (fever) and sip fluids if your throat feels sore from coughing. Products that contain codeine may help to stop you coughing but often have unwanted side-effects like constipation and drowsiness.
What is the outlook (prognosis)?
This depends on the underlying cause but is generally very good. People with smoking-related diseases who continue to smoke tend to be affected by coughing and breathlessness. These smoking-related diseases tend to get worse as time goes on. However, most coughs are due to short-lived viral infections, do not need special treatment and should be better within one to three weeks.
Further reading and references
; British Thoracic Society (2006)
; European Respiratory Society (2007)
; NICE Clinical Guideline (July 2008)
; British Thoracic Society Cough Guideline Group (2008)
; NICE CKS, June 2015 (UK access only)
; Medicines and Healthcare products Regulatory Agency (MHRA), 2009
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