Pollution Or Seasonal Allergy? How To Identify What's Triggering Your Cough

With the onset of the winter season, there is a seasonal rise in air pollution. Inhaling pollutants triggers cough and other respiratory symptoms. When you breathe in polluted air containing particulate matter like PM2.5 and PM10 or irritant gases such as ozone, nitrogen dioxide, and sulfur dioxide, your respiratory tract initiates a series of defence mechanisms. However, a drop in temperature during seasonal change also triggers overlapping symptoms.

Pollution or seasonal allergy: How to spot the difference

A persistent cough at the change of season is usually blamed on pollution or allergies. Both affect the airways, but they are handled differently. So it is worth working out which one it is.

Symptoms of pollution-related cough

Pollution-related cough comes from fine particulate matter, smoke, dust and vehicle exhaust. It is usually a dry cough with throat irritation and burning or watering eyes. Some people also get wheezing or breathlessness. It gets worse after time outdoors on poor AQI days and tends to ease after a day indoors in a closed room with an air purifier. There is usually no fever. People with asthma or COPD often see a flare-up.

There is no truly safe level of pollution. Studies show harm in sensitive groups starting in the moderate AQI band of 51 to 100. A large Korean study of over a million people found that hospital visits for asthma and COPD start rising at a daily PM2.5 of about 24 to 26 micrograms per cubic metre. Indian cities in winter often run at several times that. So a cough on a moderate AQI day can still be pollution.

Symptoms of seasonal allergies

Seasonal allergies are triggered by pollen, dust mites and mould. Sneezing, a runny or blocked nose, itchy eyes and bouts of coughing are typical. The symptoms tend to come back at the same time each year, or after contact with a specific trigger. In some people, the allergy reaches the lower airways and sets off asthma.

Flu and other viral infections

There is a third cause that is often missed. Winter is also the season for flu and other viral infections. Fever, body ache, a sore throat that came on suddenly and coloured sputum point to an infection. These symptoms follow their own course regardless of the AQI.

The lines are not always clean. Pollution makes allergic inflammation worse, and both can be present at the same time. A cough that does not settle when the weather changes, or when you stay indoors, should not be written off as seasonal.

A doctor will start with the history: how long the cough has lasted, when it gets worse, what you are exposed to and any existing conditions. Tests should follow the history. There is no blood test for pollution exposure. What tests do is measure the body's response and rule out the alternatives. For an allergic picture, a CBC with absolute eosinophil count, total IgE and specific IgE for common inhalant allergens such as dust mite, pollen and mould. Where infection is suspected, CRP and a flu or respiratory viral panel. Spirometry if asthma or airway narrowing is suspected, and a chest X-ray for a cough lasting more than three weeks.

See a doctor if a cough lasts beyond two to three weeks, if wheezing keeps coming back, or if the cough disturbs sleep. Breathlessness, chest pain, coughing up blood, sudden difficulty in breathing, or a resting oxygen reading below 94 per cent on a home pulse oximeter need prompt medical attention. In children, fast breathing, the chest pulling in while breathing or refusal to feed are urgent signs. Severe asthma attacks can become life-threatening if not treated in time.

Do not self-medicate with antibiotics, steroids or cough syrups. Identifying the trigger early guides the right treatment and helps cut repeated exposure. A cough may look like a minor seasonal problem, but one that persists or gets worse deserves attention.

(Dr. Ajay Phadke, Director, Agilus Diagnostics)

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