All you need to know about the house dust mite
Dust Mite Studies

House dust mites (HDM) were once mange mites

The house dust mite (HDM) used to be a parasite living on the skin of warm-blooded animals and has retained some parasitic properties in the enzymes it produced to digest food. In ancient times the mite's closest relative was the sheep scab mange mite, a mite that causes severe itching and allergic dermatitis in sheep and goats. That was the message from recent research published by The University of Michigan
House dust mites (HDM) used to be mange-like parasites and several of its modern allergens reflect the mite's former way of life. The most destructive of these allergens has the ability to cause the death of delicate cells protecting lungs and nasal passages. New research findings throw a different light on the house dust mite. It is not a harmless scavenger living in our homes, but a parasite that morphed to become a scavenger. The saying 'poor-little-mite' is no longer appropriate. House dust mite colonies should not be welcomed to live indoors they cause disease, promote the growth of fungi in their droppings and carry bacteria as they scavenge about in the dark. Developing children are most at risk from house dust mite exposure. Allergic asthma, rhinitis and eczema are all common childhood diseases. Beware, and Be Aware! The House Dust Mite
The House Dust Mite, London School of Hygiene and Tropical Medicine.
The house dust mite has no eyes, no respiratory system, is 75% water and has one of the smallest brains in the animal kingdom.

References

'Is Permanent Parasitism Reversible? - Critical Evidence from Early Evolution of House Dust Mites\', Pavel B Klimov, Barry O'Connor, Oxford University Press on behalf of the Society of Systemic Biologists (2013) doi: 10.1093/sysbio/syt008, Feb. 15 2013

Sheep Scab, 'Psoroptes ovis' Infestation', The Centre for Food Security and Public Health, Iowa State University, psor_a2009 on-line