The house dust mite is a very important cause of symptoms for patients with asthma, eczema, rhinitis and many other conditions.  It is not the dust mite itself that causes the main problem, but its droppings. Although just visible to the naked eye (as big as a speck of dust) it is not possible to tell by looking whether your bedding, carpets and upholstery contain the dust mite.  Sometimes there can be as many as several thousand in one gram of dust. They exist in the same places as we do, and spend live in exactly the places where we spend most of our time.  Why is this?  It is because they like to live in the same sort of conditions of warmth and moisture as we do, and they live on the scales of skin that we constantly shed. So what can we do about it.

Ventilation

Anything that you can do to get fresh air circulating the house will help.  In particular leave a window slightly ajar in the bedroom at night, with the bedroom door shut. Make sure there is adequate ventilation when cooking and bathing, and do not dry washing in the living areas (e.g. in front of the radiator).  If your house has a condensation problem, consider asking for professional help in resolving it.  In some cases a ventilation system that extracts air from environments in which there is high humidity (such as bathrooms and kitchens) can be an advantage.  When dusting, use a slightly damp duster, not too damp as the dust mite thrives on moisture.  The slight dampness will prevent the dust from becoming airborne.

Vacuum cleaning

The problem with old-style vacuum cleaners is that they are inefficient filters of the fine dust particles that include the dust mite faeces that cause the problem. This fine dust, invisible to the naked eye is pushed back into the room from the cleaner's exhaust. This means that vacuum cleaning with an inefficient cleaner can be worse than not vacuuming at all as the fine dust particles become airborne after vacuuming.  Several specialized cleaners are now available and more are coming on to the market all the time.  They incorporate a fine (HEPA) filter to ensure that the air returning to the room is free from the very fine particles. Before you spend a lot of money on a new cleaner, remember that vacuum cleaning on its own is not going to solve the house mite problem.

Avoidance of items that collect dust mites

A better answer for carpets is to remove them.  Studies have shown that even the most efficient vacuum cleaner only reduces the reservoir of house mites within the carpet by about a quarter.  Wooden, tiled vinyl or linoleum flooring is preferable.  If rugs are required, these should not be of the ‘pile’ variety – open weave types are preferable.  These should be taken outside to be beaten and aired in sunshine at intervals.  Remove also heavy lined curtains (use lighter ones that you can wash regularly).  Soft toys can be a big problem, especially if they share a child's bed.  Washing monthly at temperatures above 60 degrees Centigrade (or placing in the freezer overnight in a polythene bag) will control the problem.

Pillows, duvets and cushions

Ask most people when they last had their pillows, duvets and cushions washed, and most will admit that it is only the covers that ever get washed.

This means that it is likely that all (and particularly the pillows) will contain very high numbers of dust mites.  However, there is no reason why you cannot wash these items monthly in the washing machine at temperatures above 60 degrees centigrade.

Barrier Covers: 
You can achieve even better control by combining regular washing with full zip-shut covers to pillows, mattresses and duvets.  Several breathable types are now on the market.  Ideally you should apply the covers to new mattresses, duvets, pillows or cushions.  They will, however, still be effective if applied to old ones, preferably after washing (or after thorough vacuuming for the mattress).  At present there is no standard test to compare covers, although from 1998 all covers were required to carry a CE Mark (European Commission mark of quality).

Pets

Avoid if possible.  If you wish to check the benefit of avoidance, it will be necessary to find a home for your pet for at least three months before you can be sure.  Carpets and upholstery where pets used to live are best professionally cleaned (steam cleaning of carpets appears particularly effective) and may produce immediate improvement.  If you must keep a pet to which you know you are allergic, bath it once a week.  This is possible even for the cat!

Unhelpful Measures

Chemical sprays and powders

The benefits of using chemical measures (dust mite sprays and granules) are unproven as yet, and likely to be expensive if used adequately and frequently. 

Dehumidifiers

Whilst these sound like a very good idea, in practice, studies have not shown that they help reduce dust mite levels.

Professional removal of dust mites

A newly introduced service is the development of a portable, chemical free heat treatment system called a Diathermic Capsule which eliminates all house dust mites from beds, sofas, arm chairs, rugs, curtains, bedding and children’s soft toys*.  The articles to be treated are placed inside a huge thermal envelope which is set up like a small tent in a room in the customer’s house. The envelope is then connected to a heat generator which raises and maintains the temperature at 100ºC for 35 minutes.  Although relatively expensive (starting at around £100 to treat a double mattress and bedding) this is much cheaper than replacing mite infested articles and would be a good way to start a dust-mite control programme.
^{*ServiceMaster Environmental Services on 0800 626 303}