Respiratory Allergy

Respiratory allergy is the immune system reacting to harmless proteins that you breathe in. The body makes a specific antibody against the protein, and on later exposures that antibody triggers cells lining the nose and airways to release histamine and other chemicals within minutes. Blood vessels leak, the lining swells, glands pour out mucus and the airway narrows.

The nose and the lungs are one continuous airway and they behave as one. Most people with allergic asthma also have an allergic nose, and treating the nose properly improves the chest, so a doctor who asks about your nose when you came about your breathing is doing the right thing.

The common triggers in India are house dust mite, which lives in bedding and upholstery and is present all year in humid coastal cities, cockroach, animal dander, moulds in damp homes, and tree and grass pollens in their seasons. Vehicle exhaust, construction dust, burning refuse and incense do not cause the allergy but inflame the lining and make the reaction to everything else worse. The tendency runs in families alongside eczema and asthma, and it commonly begins in childhood or early adult life.

The history is the diagnosis, and testing is used to confirm it. Your doctor asks when symptoms occur across the day and across the year, whether they are worse indoors or out, what happens on holiday or at a different house, whether they follow bed-making, sweeping or handling books, and whether anyone at home keeps animals or the walls are damp. A pattern that repeats at the same time each year points one way and a year-round pattern points another.

They examine the lining of the nose with a light, looking at the colour and swelling of the turbinates and at the character of the secretions, and they check for polyps, a deviated septum and the pressure changes behind the ears that come with a blocked nose. They also listen to the chest and look at the skin, since asthma and eczema frequently accompany it.

Allergy testing is worth doing where the trigger is unclear or where avoidance or immunotherapy is being considered. A positive test in someone without matching symptoms means very little on its own, so results are always read against the story.

Antihistamines act within an hour and suit occasional or seasonal symptoms. A steroid nasal spray works on the underlying inflammation and needs two to four weeks of daily use for its full effect, so it is judged at a month and not after a week. Used correctly it is the most effective treatment for a persistently blocked nose, and the technique matters: aim the spray away from the central partition, do not sniff hard, and keep using it through the season.

Avoidance measures take weeks to show a benefit. Encasing the mattress and pillows, washing bedding weekly in hot water, removing carpets and soft toys from the bedroom and drying bedding in the sun are the measures with evidence behind them for dust mite.

Immunotherapy, where it is appropriate, is the only treatment that changes the underlying tendency. It runs for three to five years, with benefit appearing during the first year and lasting for years after the course is completed.