House dust mites
Everything you wanted to know, but were afraid to ask!
What are house dust mites?
House dust mites are arachnids (the same class of animal as spiders). They are very small creatures that live in household dust (often in bedding, furniture, fabrics, soft toys, clothing and carpets) feeding on dander (shed skin scales) that have been decomposed by fungi.
They like temperatures of around 20 to 25 degrees C and relative humidity of around 70 to 80 percent, although they can survive outside these ranges.
A typical house dust mite measures 0.2–0.3 millimeters in length, so you can’t see them without magnification. They are not parasites and don’t bite or suck blood.
Image source – Wikipedia
Why are they important?
The house dust mite is the most common allergen source in Australian and New Zealand humid regions.
Most of the allergen comes from their faecal pellets, while their body fragments also contribute. Allergen particles range in size from five to 40 microns.
Attempts to eradicate dust mites are unlikely to be successful. However, adopting a range of strategies should enable a reduction in exposure to the allergens.
Dust mites allergens do not typically remain airborne for long, but activities such as vacuuming, dusting, playing on the floor or moving about in bed will stir them up for a period.
Are you allergic to house dust mites?
It is important to identify and confirm allergens that trigger your symptoms. In many cases, you will have more than one trigger.
Allergy reduction strategies when you only think you know what your triggers are may not be effective.
Your GP, or an allergist, can conduct a skin prick test or blood allergen specific IgE (RAST) test, the results of which will be considered in conjunction with your medical history to allow both medical treatment, and the identification of strategies to minimise exposure to triggers.
Reducing your exposure
If you have a proven allergy to house dust mites, reducing your exposure is a good idea.
This involves killing house dust mites, removing the allergen they produce and reducing areas where they can live and breed.
Multiple strategies will be more effective than just one.
Around the house
- Use a damp or electrostatic cloth to dust hard surfaces, including hard floors
- Vacuum carpets and soft furnishings weekly, using a good quality vacuum cleaner (these will mostly have high efficiency particulate air (HEPA) filters)
- Ask someone else to do the vacuuming while you leave the room, as vacuuming (even with a HEPA filter vacuum) increases the amount of dust mite allergen in the air for up to 20 minutes
- Reduce indoor humidity – see our Indoor Humidity information sheet
- Clean window coverings (blinds and curtains) regularly (venetian blinds or flat blinds are easier to clean than heavy curtains. Washable curtains or external shutters are other options)
- Consider leather or vinyl lounges instead of fabric
- As well as being a source of allergens themselves, pets also contribute to dander on which the mites feed.
Washing bedding in water hotter than 55°C will kill mites and wash away the allergen they produce.
If you can’t wash in hot water, use a commercial product containing essential oils such as tea tree or eucalyptus, formulated to kill dust mites in cold water. Hot tumble drying of washed items for 10 minutes after they are dry will also kill mites.
Dry cleaning is not as effective as it will kill house dust mites but won’t remove the allergen.
In the bedroom
Steps to reduce exposure should focus on your bedroom, as a significant exposure to house dust mites is from your bed. Some useful measures are:
- Open the curtains and air your bedding in the sunshine
- Wash sheets and pillow cases weekly in water hotter than 55°C
- Cover your mattress, quilt and pillows with mite-resistant cases, and wash these regularly (a full encasement will be better than a cover)
- Use bedding products treated with an anti-microbial product like Ultra-Fresh®, Sanitized® or HealthGuard®.
- Remove untreated underlays
- Remove soft toys from the bedroom, or wash them weekly in water hotter than 55°C
- Freezing soft toys and other small items overnight kills the mites but doesn’t remove the allergen
Building or renovating
Consider appropriate measures to reduce dust mites when you are building or renovating your home. These include effective climate control and ventilation, selecting products that do not provide a dust mite friendly environment and/or are easy to clean.
Pesticides are not recommended as their effectiveness is unclear and their toxicity may present a risk. There are some safer anti-microbial products that may assist in reducing dust mites (even a eucalyptus spray may assist), although don’t expect a miracle.
Ultraviolet vacuums or cleaning services are promoted as a method of killing house dust mites. Exposing dust mites to ultraviolet light for a sufficient time will kill dust mites, but is not likely to be effective while mites are in their natural habitat such as mattresses or carpet because it requires a prolonged exposure and has inherent operational drawbacks.
An effective air purifier (most likely with a HEPA filter) will likely capture any airborne dust mite matter passing through it, but because the matter is relatively heavy, it tends not to stay airborne long.