Is it dust allergy, or something else?

What people mean when they say "dust allergy"

Almost everyone who comes to this clinic with a blocked nose has already been told, or has decided, that they have a dust allergy. It is such a common phrase in India that it sounds like a diagnosis. It isn't. It is a description of when symptoms happen — while cleaning, while making the bed, on entering a shut-up room — and at least five quite different things produce that pattern.

This matters because the treatments diverge completely. One of them responds to immunotherapy. One of them needs pest control and nothing else. One of them is not an allergy at all, and no amount of antihistamine will touch it.

The five things behind the phrase

1. House dust mite

This is the one people mean, and the one they most misunderstand. Dust mites are microscopic creatures that live on shed human skin. They do not live in the grey dust on your shelf — they live in mattresses, pillows, quilts, sofas and soft toys, and their droppings are the allergen. Humidity is what they need, which is why Hyderabad's humid months and air-conditioned bedrooms both suit them.

The giveaway is the timing. If your worst hour is the first hour after waking — sneezing in runs of ten or fifteen, a streaming then blocked nose, itchy eyes — you have spent eight hours with your face in the largest reservoir of mite allergen in the house. Mite allergy is the most common aeroallergen sensitisation across tropical regions, and it is treatable at the cause: it is the allergen for which immunotherapy is best established.

2. Storage mite

A close relative that lives in stored grain, flour, pulses and dried fruit rather than in bedding. Anyone who handles sacks of rice or dal, works in a kirana store, or keeps large open stores at home can be sensitised to these without reacting to house dust mite at all. It is rarely tested for and easy to miss.

3. Cockroach

The allergen nobody wants to discuss, and the one with the strongest association with severe childhood asthma in crowded housing. It is not about cleanliness — cockroach allergen is carried in dust between flats and persists long after the insects are gone. If a child has asthma that will not settle in an apartment block, this is worth testing. Treatment here is integrated pest management, sealing entry points and food storage; there is no immunotherapy in routine use for it.

4. Mould

Damp walls, seepage, bathroom ceilings, air-conditioner drip trays, the fortnight after the monsoon withdraws. Mould sensitisation produces exactly the same nasal symptoms and is often blamed on dust because it flares when a damp cupboard is opened.

5. Construction and road dust — which is not an allergy

Hyderabad builds relentlessly, and the particulate load near any site is high. But construction dust, cement dust and traffic particulate are irritants. They inflame an airway mechanically. They will not produce a positive allergy test, they do not respond to antihistamines in the way true allergy does, and they make every genuine allergy substantially worse. Saying so plainly is more useful than pretending a test will find it.

There is a sixth possibility worth naming: non-allergic rhinitis. Perhaps a fifth of people with persistent nasal symptoms have no allergy at all. Their noses over-respond to temperature change, strong smells, perfume, incense and pollution. Every allergy test comes back negative — which is a finding, not a failure, and it changes what is prescribed.

How we tell them apart

The history does most of the work. When did it start, what time of day is worst, what happens on holiday, what happens when it rains, is there a pet, is there damp, is there building work, does anyone else at home have it. Then a skin prick test against a panel chosen for this region — not an imported European panel heavy with grasses that barely grow here — gives an answer in about twenty minutes.

One caution that matters more than any other on this page. A positive test means your immune system recognises that substance. It does not, on its own, mean you are allergic to it. Plenty of people have positive tests to things that cause them no trouble whatever. The result and your story are read together, and neither is a diagnosis alone.

What actually helps, once you know

• For house dust mite — allergen-proof mattress and pillow covers, weekly hot-washing of bedding, removing carpets and soft toys from the bed, and controlling humidity. Then, where symptoms persist and testing confirms it, immunotherapy aimed at the cause.
• For cockroach — pest control done properly and repeatedly, sealed food storage, and fixing the water sources they come for.
• For mould — finding and fixing the damp. Cleaning the surface without stopping the seepage achieves nothing.
• For construction dust — a properly fitted N95, not a surgical or cloth mask; keeping windows closed on the site-facing side; and treating the underlying allergy hard, because that is the part that can be changed.
• For non-allergic rhinitis — saline irrigation, intranasal treatment aimed at the right mechanism, and stopping the antihistamines that were never going to work.

Next step

Find out which one it is

Testing takes about twenty minutes and is read in the same visit. Stop antihistamines for five days beforehand — including the ones inside cold and cough medicines.