Most coughs associated with a cold or viral infection improve with time. However, when a cough continues for several weeks, repeatedly returns or begins to interfere with sleep, work and conversation, simply taking another cough syrup may not solve the problem.
A persistent cough is not a diagnosis by itself. It is a symptom that can arise from the nose and sinuses, airways, lungs, stomach, medication or environmental exposure. Sometimes more than one factor is present at the same time. In Lahore, dust, traffic pollution and seasonal smog can aggravate coughing, but they should not automatically be assumed to be the only cause.
The aim of assessment is therefore not just to suppress the cough. It is to identify and treat the reason behind it.
When Does a Cough Become Persistent or Chronic?
In adults, cough is commonly classified by duration:
- Acute cough: less than three weeks
- Subacute cough: between three and eight weeks
- Chronic cough: longer than eight weeks
A cough may still require earlier assessment if it is worsening or accompanied by concerning symptoms. The eight-week definition does not mean that everyone should wait eight weeks before seeing a doctor.
For example, a prolonged cough associated with fever, night sweats, unexplained weight loss or blood in the sputum needs prompt review. This is particularly important in Pakistan, where tuberculosis remains an important and treatable cause of respiratory illness.
Why Can a Cough Continue After an Infection?
After a cold, influenza or another respiratory infection, airway inflammation and sensitivity can persist after the infection itself has resolved. Cold air, perfume, dust, laughter or prolonged talking may then trigger coughing. This is often called a post-infectious cough and it usually improves gradually.
However, an apparent infection can also uncover previously unrecognised asthma, nasal allergy or another respiratory condition. A cough that is not improving as expected, or that repeatedly returns after every respiratory infection, deserves a more careful assessment.
Common Causes of Persistent Cough
1. Nasal allergy, sinus inflammation and postnasal symptoms
Inflammation of the nose and sinuses can be associated with nasal blockage, sneezing, watery discharge, an itchy nose, frequent throat clearing or a sensation of mucus in the throat. Symptoms may worsen with dust, pollen, mould, animal exposure or changes in weather.
Not every patient feels obvious mucus dripping down the throat. Examination and, where appropriate, allergy assessment can help determine whether upper-airway disease is contributing to the cough.
2. Asthma and eosinophilic airway inflammation
Asthma does not always present with obvious wheezing. In some people, cough is the main symptom. Clues can include coughing at night, symptoms after exercise, chest tightness, wheezing, or coughing triggered by cold air, dust, perfume or pollution.
Spirometry can demonstrate variable airflow obstruction in some patients, but normal spirometry on one occasion does not exclude asthma. Depending on the clinical situation, assessment may include bronchodilator testing, fractional exhaled nitric oxide (FeNO), blood eosinophils or a bronchial challenge test.
Another condition, eosinophilic bronchitis, can cause chronic cough without the typical airflow obstruction seen in asthma. This is one reason why treatment should be guided by clinical assessment rather than symptoms alone.
3. Gastro-oesophageal reflux
Reflux can contribute to coughing in some patients, particularly when there is heartburn, acid regurgitation, throat symptoms or coughing after meals or on lying down. However, many people with chronic cough do not improve with acid-suppressing medication, and cough should not automatically be attributed to “silent reflux.”
The history should guide whether reflux is a likely treatable contributor. Long courses of medication should not be started solely on the assumption that every unexplained cough comes from the stomach.
4. Smoking, vaping and environmental irritation
Cigarette smoke, vaping aerosols, shisha, second-hand smoke, workplace dust and chemical fumes can irritate the airways and sustain a cough. Long-term smoking also increases the risk of chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer.
Avoiding exposure is important, but a new or changing cough in a smoker or former smoker still requires appropriate medical evaluation.
5. Medication-related cough
Some blood-pressure medicines called angiotensin-converting enzyme inhibitors, or ACE inhibitors, can produce a persistent dry cough. Examples include ramipril, lisinopril, enalapril and perindopril.
The cough may begin soon after starting treatment or appear months later. Do not stop a prescribed blood-pressure medicine yourself. Discuss it with the prescribing clinician, who can decide whether an alternative is appropriate. Improvement may not be immediate after the medicine is changed.
6. Chronic lung conditions
COPD, bronchiectasis, interstitial lung disease and other respiratory disorders may cause ongoing cough, sometimes with sputum or breathlessness. Previous tuberculosis can leave airway damage or scarring that contributes to recurrent symptoms.
Initial spirometry may be helpful, while selected patients require complete pulmonary function tests, including lung-volume measurement and diffusion capacity, to assess lung physiology more fully.
7. Tuberculosis and other infections
Tuberculosis should be considered when a prolonged cough is accompanied by sputum, fever, night sweats, weight loss, chest pain, blood in the sputum or relevant exposure. Symptoms can sometimes be mild, so clinical judgement remains important.
Evaluation may require chest imaging and appropriate sputum or molecular testing. Tuberculosis is treatable, but early diagnosis matters for both the patient and close contacts. Ordinary antibiotics or repeated cough mixtures do not provide adequate treatment for TB.
8. Cough hypersensitivity
In some patients, coughing continues even after the common underlying causes have been investigated or treated. The cough reflex may become unusually sensitive, with talking, laughing, perfumes, temperature changes or a minor throat sensation provoking repeated bouts of coughing.
This is increasingly recognised as cough hypersensitivity. It does not mean that the symptoms are imagined. Specialist assessment is needed before labelling a cough unexplained or refractory, because treatable conditions and warning signs must first be considered.
Can Lahore’s Pollution and Smog Cause a Lasting Cough?
Air pollution can irritate the nose, throat and airways, aggravate asthma and COPD, and increase respiratory symptoms. Lahore’s dust, traffic emissions and winter smog may therefore trigger coughing or make an existing respiratory condition more difficult to control.
People with asthma, COPD, heart disease, advanced age, pregnancy or other vulnerabilities may be affected more severely. On days with poor air quality, reducing unnecessary outdoor exposure, avoiding outdoor exercise near busy roads and using a properly fitted particulate respirator when exposure cannot be avoided may help reduce inhalation of fine particles.
Nevertheless, it is unsafe to assume that every persistent cough is “just smog.” Pollution may be the trigger, an aggravating factor or only one part of the problem. A cough that continues when pollution improves, wakes you repeatedly, produces blood or is associated with breathlessness, weight loss or fever should be assessed.
Does a Dry or Productive Cough Reveal the Cause?
The character of the cough provides clues, but it rarely establishes the diagnosis by itself.
A dry cough may occur with asthma, post-infectious airway sensitivity, medication effects, reflux or interstitial lung disease. A productive cough may occur with infection, bronchiectasis or chronic bronchitis. The colour of sputum alone cannot reliably determine whether an infection is viral or bacterial, and green or yellow sputum does not automatically mean that antibiotics are required.
Changes from the patient’s usual pattern are often more informative. Increasing sputum volume, a new unpleasant smell, blood, fever or worsening breathlessness should be discussed with a clinician.
Warning Signs That Need Prompt Medical Assessment
Seek timely medical attention if a cough is accompanied by:
- Blood in the sputum
- Increasing or unexplained breathlessness
- Chest pain, fainting or low oxygen readings
- Persistent fever or night sweats
- Unexplained weight loss or loss of appetite
- New hoarseness or difficulty swallowing
- Recurrent pneumonia or repeated chest infections
- Significant immune suppression
- A new or changing cough in a smoker or former smoker
- An abnormal chest X-ray or CT scan
Severe breathing difficulty, blue discolouration, confusion, significant coughing of blood or severe chest pain requires urgent or emergency assessment.
How Does a Pulmonologist Investigate Persistent Cough?
There is no single “chronic cough test.” The investigation depends on the history, examination, age, exposures and associated symptoms.
Clinical history and examination
Useful details include when the cough began, whether it is dry or productive, triggers, night-time symptoms, nasal and reflux symptoms, smoking or vaping, occupational exposure, medication use, previous tuberculosis and any accompanying breathlessness, fever or weight loss.
Chest imaging
A chest X-ray is commonly considered when cough persists or when there are concerning clinical features. A normal X-ray is reassuring but does not exclude asthma, eosinophilic airway disease, reflux-related symptoms or every early lung condition. CT scanning is reserved for patients in whom the history, examination, X-ray or subsequent course provides an appropriate indication.
Spirometry and other breathing tests
Spirometry assesses airflow and can help identify asthma or COPD. Bronchodilator testing evaluates whether airflow improves after an inhaled medicine. If symptoms remain unexplained or a more detailed physiological assessment is required, full pulmonary function testing may assess lung volumes and gas transfer.
FeNO, eosinophils and allergy assessment
FeNO and blood eosinophils can provide evidence of eosinophilic or type 2 airway inflammation in the correct clinical context. Skin aeroallergen testing may be useful when symptoms and exposure history suggest respiratory allergy. A positive allergy test must be interpreted alongside the patient’s symptoms; sensitisation alone does not prove that an allergen is responsible for the cough.
Sputum and infection testing
Patients with productive cough, recurrent infections or features suggesting tuberculosis may require sputum examination, microbiology or molecular testing. The tests selected depend on the clinical picture.
Further specialist tests
Bronchial challenge testing, CT imaging, bronchoscopy, cardiac assessment or evaluation by an ear, nose and throat or gastroenterology specialist may be appropriate in selected patients. These are not required routinely for everyone with a cough.
Why Cough Syrups and Repeated Antibiotics May Not Solve the Problem
Cough medicines may occasionally provide short-term symptom relief, but they do not treat asthma, nasal inflammation, tuberculosis, bronchiectasis, medication-related cough or cough hypersensitivity.
Likewise, antibiotics only help selected bacterial infections. Repeated empirical antibiotic courses can cause adverse effects and contribute to antimicrobial resistance while delaying the correct diagnosis. Steroid tablets and inhalers also should not be started repeatedly without a clear clinical reason and follow-up plan.
The most effective treatment depends on identifying the likely cause or treatable traits and then reviewing whether the targeted treatment has actually worked.
What Can You Do While Waiting for Assessment?
- Avoid smoking, vaping, shisha and second-hand smoke.
- Reduce exposure to dust, perfume, incense and chemical fumes when they trigger symptoms.
- Monitor air quality and limit strenuous outdoor activity during severe pollution.
- Keep adequately hydrated.
- Record when the cough occurs, its triggers and any associated wheezing, nasal symptoms, reflux, fever or sputum.
- Bring a complete medication list and previous chest imaging or lung-test reports to the appointment.
- Do not stop prescribed medication or begin antibiotics, steroids or inhalers without appropriate advice.
When Should You Book a Pulmonology Assessment?
Arrange an assessment if the cough is not improving after several weeks, repeatedly returns, interferes with sleep or daily activity, or occurs with wheezing, breathlessness, sputum or other concerning symptoms. Earlier review is appropriate when warning signs are present.
At Australian Polyclinic, persistent cough can be assessed alongside access to spirometry, comprehensive pulmonary function testing, FeNO, allergy testing and other investigations when clinically indicated. Testing is selected according to the individual patient rather than using the same package for everyone.
Appointments: Australian Polyclinic, First Floor, Building 19, CCA, DHA Phase 5, Lahore
Phone: +92 311 057 3333
Frequently Asked Questions
How long should a cough last before I see a doctor?
Many coughs following a viral infection improve gradually, but assessment is reasonable if a cough is not improving after several weeks, repeatedly returns or affects sleep and daily activity. Do not wait if there is coughing of blood, breathlessness, chest pain, fever, night sweats, weight loss or another warning sign. In adults, a cough lasting more than eight weeks is classified as chronic.
How can I tell whether my cough is caused by allergy or asthma?
Allergy is more likely when coughing occurs with sneezing, an itchy or blocked nose, watery discharge or clear exposure-related symptoms. Asthma may cause night-time cough, wheezing, chest tightness or symptoms triggered by exercise, cold air, dust or perfume. The patterns overlap, so spirometry, FeNO or allergy testing may be required in selected patients.
Is a normal chest X-ray enough to rule out the cause of chronic cough?
No. A normal chest X-ray is reassuring, but conditions such as asthma, eosinophilic airway inflammation, nasal disease, reflux-related symptoms and cough hypersensitivity may still be present. Further testing should be guided by the history and examination.
Do I need antibiotics for yellow or green sputum?
Not necessarily. Sputum colour alone cannot reliably distinguish a bacterial infection from other causes. Antibiotics should be prescribed when the overall clinical assessment supports a bacterial infection or another specific indication.
Can Lahore smog cause persistent cough?
Air pollution can irritate the airways and worsen asthma, COPD and respiratory symptoms. However, a cough that continues, repeatedly returns or occurs with warning signs should not automatically be attributed to smog without assessment.
Which tests are used to investigate persistent cough?
Depending on the patient, assessment may include a chest X-ray, spirometry with bronchodilator testing, FeNO, blood eosinophils, allergy testing, sputum studies or complete pulmonary function tests. CT scanning, bronchial challenge or bronchoscopy is reserved for selected clinical indications.
Medical Disclaimer
This article provides general educational information and is not a substitute for individual medical advice, examination, diagnosis or treatment. Do not start, stop or change prescribed medicines on the basis of this article. Seek urgent medical attention for severe breathing difficulty, significant coughing of blood, severe chest pain, blue discolouration, fainting or confusion.
Written by: Australian Polyclinic Medical Team
Medically reviewed by: Dr G. Sarwar Chaudhry, MBBS, FRACP (Australia), FCCP (USA)
Consultant Pulmonologist and Sleep Physician
Last reviewed: 27 August 2026
Clinical references
- British Thoracic Society. BTS Clinical Statement on Chronic Cough in Adults. Thorax. 2023;78(Suppl 6)–s19. https://www.brit-thoracic.org.uk/clinical-resources/clinical-statements/chronic-cough-in-adults/
- European Respiratory Society. ERS Guidelines on the Diagnosis and Treatment of Chronic Cough in Adults and Children. European Respiratory Journal. 2020;55:1901136. https://publications.ersnet.org/content/erj/55/1/1901136
- World Health Organization. Tuberculosis: Fact Sheet. https://www.who.int/news-room/fact-sheets/detail/tuberculosis
- World Health Organization. Health Impacts of Air Pollution. https://www.who.int/teams/environment-climate-change-and-health/air-quality-energy-and-health/health-impacts