All about house dust mite droppings

The average intact mite dropping is 10 to 40 microns in size. However, in one research paper scientists observed airborne particles containing mite allergens that ranged from 5 to 40 microns. These were described as either faeces, fibres or flakes of translucent particles.

There may be over 14 separate, fully identified allergens, within one dropping. The latest identified allergen (Der p23) is part of the film that covers the mite's dropping and is consider to be highly allergenic.

To date scientists have identified over 7 different active enzymes from house dust mites.

Particle size matters for people who are sensitive to house dust mites because the smaller the faecal particle carrying active enzymes, the deeper it can travel into the lungs, even reaching delicate areas of gas exchange.

Section of the human lung

In general, inhaled particles above 10 microns will land on the trachea or bronchi while smaller dust (below 10 microns) has the potential to reach and be deposited in the alveoli. The alveoli is the last stop in the branches of our lungs and where gases are exchanged.