Dust mites are the bane of allergic people’s existence from the time that they first developed allergic symptoms onwards. As one of those allergic people, I’m intensely interested in dust mites in the same way that the Coke is interested in Pepsi – I want to know my enemy. So, I researched a dust mite dossier. Here’s the fruits of my labour – all you need to know about allergenic dust mites.
What are dust mites?
Dust mites are considered the leading cause of year-round asthma allergy symptoms worldwide.
Dust mites were first discovered in 1694 by the inventor of the microscope, Anton van Leeuwenhoek, who described ‘little animals’ he saw in household dust.
Dust Mites are members of the Arachnid class alongside, spiders, ticks, scorpions & other mites etc. and bear a resemblance to ticks. Arachnids (Class: Arachnida) are technically not insects (Insecta) and evolved earlier. Our immune systems have been dealing with dust mites throughout the evolution of humans.
Dust mites are approximately a quarter of a millimetre long. Theoretically, dust mites are big enough to see with the naked eye, but I’ve never managed to clap eyes on one. To see the details of a dust mite, you need 10X magnification. An average magnifying glass offers about 2x to 6x magnification. The little buggers may as well be microscopic.
Dust Mites are Tough
I like to think of dust mites as the Bruce Willis of household pests. They die hard.
- Dust mites are too small to squash.
- Bleach and strong soaps won’t kill dust mites.
- It takes exposure to temperatures of above 60 degrees celsius (140 Fahrenheit) for an hour to kill dust mites.
- Dust mites reproduce very quickly.
Dust Mite Life Cycle and Reproductive Capacity
- Male Dust Mites live 10-19 days.
- A pregnant female dust mite lives up to 70 days and lays 60-100 eggs. On average female dust mites add 25-30 mites to the population per week.
- There can be over 3500 mites in a gram of dust. (Boquete et al. 2006) This figure is from a Spanish study of 3 dust mite species in the most humid month of their year, so it’s a maximum. Dust mite populations wax and wane seasonally with humidity. In Sydney, my home city, dust mites likely peak in February, our most humid month.
It should be noted that these lifespans and fertility rates vary between dust mite species, these figures refer to Dermatophagoides pteronyssinus, the European Dust Mite. A big player in the dust mite world.
Dust Mite Allergen:
Dust mites produce strong enzymes (proteases) to digest their food. Allergic people react to dust mite enzymes surviving in:
- Dust mite faeces (poo!).
- Enzyme-coated, partially-digested dust particles.
- Moulted dust mite skin (exuviae). D
Multiple dust mite enzymes causing allergic symptoms have been identified across different mite species. These enzymes serve various metabolic functions for the mites (Thomas, W. et. al, 2002)
Dust mites go to the toilet a lot, averaging about 20 droppings a day, eventually producing 2000 times their body weight in the course of their life. That’s pretty productive! By way of comparison, humans produce about 440 times our body weight over our lifespan. Unfortunately, dust mite faeces will still still cause an allergic reaction after the mite is dead and departed.
Fun fact: It’s possible to smell the proteins (enzymes) that dust mites produce in vacuum cleaner bags.
Which Dust Mites Are The Most Allergenic?
Mites (Sub-class: Acari) are very diverse and successful, it’s estimated that 48,200 have been described, most of which are microscopic. The bulk of dust mite research has occurred in countries other than Australia and is mainly focused on 2 species of dust mites that have been identified as primary culprits in causing allergic reactions.
The two main allergenic house dust mites are Dermatophagoides pteronyssinus (the European Dust Mite) & Dermatophagoides farinae (the American Dust Mite). Pteronyssinus is the most common type of dust mite found in Australia and is known to cause allergic symptoms. The European mite prefers higher humidity and therefore, coastal areas in Australia. Dermatophagoides farinae prefer drier areas and are less common in Australia.
Euroglyphus Maynei is another dust mite species that is distributed widely through humid geographical areas (tropics and sub-tropics) and is also allergenic, but is not as well researched as the two Dermatophagoides species mentioned above. It’s an important mite in the Americas.
Dust Mite Predators
Their predators are another allergenic mite, the Hunting Mite (Cheyletus eruditus), silver fish and pseudoscorpions. The Hunting Mite has been actually used as a biological control for storage mites in grain stores. It’s not super-effective bio-control because periods of high humidity allow the pest species’ populations to expand well beyond Cheyletus’ ability to hold them down.
By the way, ‘Dermatophagoides’ means ‘skin eating’ which is pretty self-explanatory, but ‘Euroglyphus’ seems to mean ‘European carver’ which eludes explanation from me!
Dust Mite References
Thomas, Wayne R., Wendy-Anne Smith, Belinda J. Hales, Kristina L. Mills, and Richard M.O’Brien. “Characterization and Immunobiology of House Dust Mite Allergens.” International Archives of Allergy and Immunology 129.1 (2002): 1-18. Print.
Boquete, M., Iraola, V., Fern\’, ez-Caldas, E., Villaroel, L., Carballada, F., de la Cuesta, C., Lopez-Rico, M., Orjales, R., Parra, A., Soto-Mera, M. and others, (2006). House dust mite species and allergen levels in Galicia, Spain: a cross-sectional, multicenter, comparative study. Journal of Investigational Allergology and Clinical Immunology, 16(3), p.169.