Dust mites are tiny, eight-legged arachnids of the spider family measuring less than a fraction of a millimetre in size and are the major cause of allergic reactions.

House dust mites survive on shed human skin scales. As these mites digest their food, they produce potent allergens which are released in their fecal pellets (droppings). Inhaling these microscopic pellets and parts of dead mites provokes allergic symptoms such as nasal congestion, itching, watery eyes, sneezing and asthma.