Every winter the same thing happens across a band of the world from Lahore and Delhi to Hanoi, Jakarta, Cairo, Mexico City and Santiago: the air thickens, and within days clinics fill with people carrying the same complaint. A dry cough that will not settle. Eyes that burn. A throat that feels scraped. A chest that will not take a full breath.
Delhi and the wider National Capital Region are in the worst of it right now. The daily average air quality index hit 382 on 6 November, which triggered Stage III of the Graded Response Action Plan across the NCR, and several stations recorded readings in the 450 to 476 range in the days after Diwali. Forecasts this week point at the severe band again. If you are reading this somewhere with clean air today, keep the piece anyway, because wildfire smoke now delivers the same exposure to cities that never used to see it.
Air quality indexes are mostly driven by PM2.5, particles smaller than 2.5 micrometres across. For scale, a human hair is about thirty times wider.
That size is the whole problem. Your nose and upper airway are built to trap large particles, and they do it well. PM2.5 goes straight past those defences, down to the alveoli where oxygen crosses into your blood, and the smallest fraction crosses with it. So this is not only a lung exposure. It is a whole body exposure that reaches your blood vessels, your heart and your brain, which is why the World Health Organization treats air pollution as one of the largest environmental threats to health rather than as a lung issue.
In the airway it triggers inflammation, extra mucus and twitchy, narrowed tubes. That combination produces the specific cluster of symptoms people search for every November.
This is the question that sends people to a search engine at eleven at night, and there are five practical ways to separate them.
Fever and body aches point at infection. Pollution does not give you a temperature. If you are feverish, aching and shivery, look at flu, COVID and RSV instead.
Check whether it tracks the air, not the week. Pollution symptoms rise and fall with the index. Better on a windy day, worse after a still night, worse on the commute. Infections follow their own arc regardless of the weather. If you are not sure what the numbers mean, AirNow explains each AQI band and what it is supposed to change about your day.
See what happens when you leave. If two days in a cleaner city, or a weekend in a room with a filter running, clears your throat and your eyes, that is your answer.
Count the household. Viruses move through a family in sequence over a week. Pollution hits everyone in the house on the same day, and hits the asthmatic and the youngest hardest.
Watch the eyes. Burning, stinging eyes alongside a cough is far more typical of irritant exposure than of a cold.
Children, people over 65, pregnant women, anyone with asthma, COPD, heart disease or diabetes, and outdoor workers feel all of this sooner and harder. If you are in one of those groups, treat the first symptoms as a reason to change what you do that day rather than something to push through.
Start a symptom search and three medical AI models will take your symptoms, ask the follow-up questions a clinician would, and cross-check each other before giving you an answer. It is free, private and takes about a minute.
Wear the right mask. A properly fitted N95, KN95 or FFP2 filters fine particles. A cloth mask and a loose surgical mask do close to nothing for PM2.5. Fit matters as much as the rating: a gap at the nose bridge or a mask under the nose is an unfiltered mask.
Filter the air where you sleep. You spend a third of your day in one room, which makes the bedroom the cheapest win. A HEPA purifier sized for the room, run with the door and windows closed, drops indoor PM2.5 substantially. Keep the filters changed, because a clogged filter is an expensive fan.
Move your exercise. Hard exercise multiplies how much air you pull in and switches you to mouth breathing, which bypasses your nose entirely. On a severe day, exercise indoors or skip it. A run in that air costs you more than it gives you.
Time your outdoor hours. Particle levels usually peak overnight and in the early morning when the air is still, and ease by mid afternoon. Check the index before the school run rather than after it.
Keep indoor sources down. Indoor smoking, incense, mosquito coils, unvented cooking and candles all raise indoor PM2.5. Use the kitchen extractor every time.
If you use inhalers, carry them and use the preventer. Air pollution season is when preventer adherence matters most, and it is exactly when people run out.
Steam inhalation soothes a throat but removes nothing from your lungs. Houseplants do not meaningfully clean indoor air at the rates sold to you. Detox drinks, juices and jaggery do not remove particles from your body. A mask worn below the nose protects nobody, and a dust mask from a hardware shop is not an N95 unless it says so.
The cough is the symptom. The risk is cardiovascular. As the American Lung Association sets out, long-term exposure to fine particles raises the risk of heart attack, stroke, high blood pressure, type 2 diabetes and reduced lung growth in children, and the effect is cumulative rather than something you shake off in spring.
That sounds fatalistic and it is not. Exposure is a dose, and dose is the one part you control. Lower peak exposure on the worst days, clean air in the room you sleep in, a correctly fitted mask when you are outside, and exercise moved indoors during the severe band all reduce that dose meaningfully.
Pollution symptoms look like a cold without the fever, track the air quality index rather than the calendar, and hit the whole household at once. Fit an N95, filter your bedroom, move exercise indoors on severe days, and check the index before you plan your morning. If there is fever, blood, chest pain or breathlessness at rest, that is no longer about the air.
Start a symptom search if you are not sure whether this is the smog or an infection, and keep the episodes in your Health Passport so that next winter you can see which exposures actually set you off.
This article is for general education and is not a substitute for professional medical advice. Air quality figures reflect early November 2026 and change daily. Anyone with asthma, COPD or heart disease should have a personalised action plan from their own clinician.
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