Dust mites

What is actually happening

Eight hours a night in a bed, four or five in the same chair. To a mite population that is a steady food supply in the two or three places a household uses most, which is why somebody reacting at night and feeling better during the day is often reacting to where they sleep rather than to the carpet. Carpet holds its share and holds it down in the fibre, out of the air, which is the filter argument — but the mattress is usually the larger single reservoir in a bedroom.

How you prevent it

Take the food supply away rather than chasing what it produces. Vacuum the bare mattress every time the sheets come off, which is the only moment the surface is accessible and takes about a minute. Vacuum the couch and the usual chair weekly. Then have the oils and trapped debris extracted out of carpet, upholstery and mattresses on a cycle. Spiker makes no allergen-percentage or health-outcome claims about any of this — the mechanism is checkable, a result is not.

In the surfaces people spend the most uninterrupted hours pressed against — mattresses and soft furniture more than the floor. They feed on the dead skin we shed, and it is their microscopic waste that becomes airborne. That is why the reservoir concentrates where the shedding happens.