A Persistent Cough

Most new coughs follow a viral infection and improve within several weeks. A cough lasting more than three weeks should be reviewed, but that threshold does not automatically mean chronic disease, lung cancer or a need for a chest X ray.

A cough is a reflex and a symptom A cough is a protective reflex that can clear mucus, inhaled material or irritants from the throat and airways. It can also become troublesome when the cough pathway remains sensitive after the original trigger has settled. A persistent cough is a symptom rather than a diagnosis. Its sound, dryness or timing cannot identify the cause by itself. Duration helps, but it is not the whole assessment In adults, an acute cough lasts less than three weeks. It is commonly caused by a viral respiratory infection and often improves without antibiotics. NICE advises that an acute cough can take three to four weeks to settle. This means a cough crossing three weeks is not automatically serious or chronic. The NHS still advises arranging a GP review when a cough lasts more than three weeks. This is a public safety threshold for assessment, not an automatic instruction to have a chest X ray. In adults, chronic cough usually means a cough lasting more than eight weeks. In children, chronic cough is often defined as lasting more than four weeks, and the likely causes differ from those in adults. These time ranges organise the assessment. They do not replace consideration of severity, age, associated symptoms or risk factors. The pattern provides additional clues Clinicians ask whether the cough is dry or productive. A productive cough brings up sputum, which is mucus from the lower airways. The amount, thickness and presence of blood can matter. The medical term for coughing up blood is haemoptysis. In an otherwise uncomplicated acute cough, yellow or green sputum alone does not reliably distinguish bacterial from viral infection or determine whether antibiotics are needed. Timing can also help. A cough may follow an infection, occur at night, worsen with exercise, appear after meals or lying down, or relate to work and environmental exposure. Clinicians ask about fever, wheeze, breathlessness, chest pain, hoarseness, repeated infections, appetite change, weight loss and night sweats. They also ask about smoking, vaping, asbestos, medicines and recent travel or infection exposure. A sudden cough after choking raises concern about inhaled material, especially in a child. A cough that comes in repeated bursts with vomiting or a whooping sound may suggest whooping cough, but testing and assessment may still be needed. Several processes can keep a cough going A recent viral infection is a common cause of a new cough. The airway nerves can remain sensitive for several weeks after the infection itself improves. Asthma and other airway conditions can cause cough, sometimes with wheeze or breathlessness. Symptoms alone do not confirm asthma, and objective testing may be needed. Smoking, vaping, air pollution and workplace irritants can repeatedly stimulate the cough pathway. Chronic productive cough needs assessment for airway disease, infection or widened, damaged airways called bronchiectasis. Long lasting inflammation of the nose and sinuses can contribute when cough occurs with persistent nasal blockage or discharge. Gastro oesophageal reflux may contribute when heartburn or stomach contents coming back up are present. Treating reflux without typical reflux symptoms often does not improve chronic cough. The presence of reflux or nasal symptoms does not prove that either is the main cause. An ACE inhibitor can cause a persistent dry cough. Do not stop a prescribed medicine yourself, because a clinician may need to confirm the medicine and arrange a suitable alternative. Some adults develop cough hypersensitivity. Harmless triggers such as perfume, cold air, talking or laughing then provoke coughing more easily than expected. Less common causes include tuberculosis, lung scarring conditions, heart failure and lung cancer. A cough may also have more than one contributor. Children require a child specific approach. A persistent wet cough, poor growth, recurrent pneumonia, coughing with feeding or a sudden onset after choking needs particular attention. Examination gives clues rather than a complete answer A clinician checks breathing rate, oxygen saturation, pulse, temperature and general appearance. They listen for wheeze, crackles, reduced air entry or other chest sounds. They may examine the nose, throat, neck and heart and check weight or signs of fluid retention. A normal examination does not exclude every important or intermittent cause. The cough sound alone is rarely diagnostic. Even a distinctive pattern must be interpreted with what the person describes, the examination and appropriate tests. Tests are selected for a reason A chest X ray can show some infections, masses, fluid, lung collapse or other structural changes. It does not show every cause of cough, and a normal result does not completely exclude lung cancer. A chest X ray is not automatically required because a cough has crossed three weeks. The decision depends on age, smoking or asbestos exposure, associated symptoms, examination findings and the duration and character of the cough. NICE recommends an urgent chest X ray for certain people aged 40 or over. This includes an unexplained cough in someone who has ever smoked, or an unexplained cough with another listed symptom such as weight loss or breathlessness. For adult chronic cough lasting more than eight weeks, the British Thoracic Society recommends a structured assessment. Basic tests include a chest X ray, a blood count and spirometry, with FeNO where available and other tests selected from the pattern. Spirometry measures airflow. FeNO estimates nitric oxide in exhaled air and can support assessment for airway inflammation often linked with asthma. Neither test diagnoses the cause alone. A sputum sample may be tested when infection is suspected. More detailed scans or specialist tests are used only when the assessment raises a specific question. Children follow a different investigation pathway. A persistent wet cough or other concerning features may need paediatric assessment rather than the adult chronic cough sequence. What may happen after assessment A short cough after a cold, without concerning features, is often managed with self care and clear follow up advice. Antibiotics are not routinely needed for an uncomplicated acute cough or acute bronchitis. A cough lasting more than three weeks should be reviewed by a GP. The clinician may monitor, investigate or refer depending on the whole pattern rather than the calendar alone. An unexplained persistent cough with past or current smoking, weight loss, breathlessness or another concerning feature may need prompt imaging. Further assessment may still be needed if the chest X ray is normal but concern remains. When to get help Call 999 or go to A&E if you cough up more than a few spots or streaks of blood. Also call 999 if blood occurs with difficulty breathing, a very fast heartbeat, or pain in the chest or upper back. Call 999 for severe breathing difficulty, blue or grey skin, sudden confusion, collapse or reduced responsiveness. Do not drive yourself to A&E. Ask for an urgent GP appointment or contact NHS 111 if the cough is very bad, quickly worsening or impossible to stop. Seek urgent advice if you feel very unwell, have chest pain, find breathing difficult or cough up a few spots of blood. Arrange a GP review if the cough lasts more than three weeks, keeps returning or accompanies unexplained weight loss. Review is also important with a weakened immune system or a long term heart or lung condition. For a child, call 999 if they are finding it hard to breathe. Arrange GP assessment for a cough lasting more than three weeks or sooner if feeding, growth or general condition is affected. This lesson explains how clinicians assess a persistent cough. It cannot identify the cause of an individual cough or replace urgent medical help.

Three weeks is a public review threshold, not an automatic diagnosis or investigation rule. Persistent cough is assessed through duration, age, pattern, associated features, risks, examination and targeted tests.