Features - Dust Mites by Dr R Turner

House dust is the major cause of allergy in people with year long runny or blocked nose and/or sneezing. In addition to these allergic reactions, dust can trigger and irritate asthma and eczema.

Only since 1964 has it been recognised that the house dust mite can cause problems. A speck of dust may contain fabric fibres, human skin, bacteria, animal danders, pollen, grains, moulds spores, food particles and mites.

What are dust mites like?

Dust mites cannot be seen without a microscope. They thrive in warm and humid conditions. Because they feed on skin scales, they love bedding, carpets, upholstered furniture, clothing, closets and car seats. They usually survive ordinary vacuuming because they burrow deep and are equipped with sucking pads on their feet.

People become allergic to the proteins in the mite faecel pellets. As many as 3000 mites have been counted in a gram of dust, although the average is around 250-300. Each mite produces 10-20 faecal particles per day. Their lifecycle from egg to adult is 30 days and each egg laying female mite can increase the population by 40-80 every six weeks!

Studies in London show that mite populations peak from December to March, ie times of high household humidity.

How is allergy to dust mites diagnosed?

By medical history and skin testing. A positive reaction is characterised by a raised weal circled by redness - the larger the weal, the greater the allergy.

What can be done to help alleviate the symptoms?

Dust mites are difficult to eradicate. An anti-dust programme will help to reduce the symptoms, but intensive vacuuming is needed to remove significant amounts of dust from carpets.

The home needs to be thoroughly cleaned on a regular basis by frequent vacuuming and dusting with a damp cloth. Sprays used on carpets and mattresses can also help.

Dust control in the bedroom

The highest concentration of mites occur in the bedroom, especially in the mattress and bedding.

Mattresses, duvets and pillows should be enclosed in non-allergenic covers. These have been developed to allow the passage of water vapour whilst excluding the dust mites.

In summer take the mattress outside (take off the cover) and give it a good beating. Air duvets in sunlight (ultraviolet light is harmful to mites. Also, wash duvets and pillows in the washing machine.

Avoid fabric headboards as mites thrive in these, and don't let children jump up and down on the bed as this disturbs the allergen in the mattress. Stuffed animals harbour mites so wash them regularly. Avoid bunk beds or at least never let your allergic child sleep in the bottom bunk.

Put clothes away in cupboards and drawers and don't hang dressing gowns on the back of the door as they will collect dust.

WASH CLOTHES AND BEDDING IN A HOT WASH OF AT LEAST 60 DEGREES AS THIS WILL KILL THE MITES.

Other dust prevention

Carpets - they provide a breeding ground for mites. Choose short pile carpets or rugs and if you decide to have a wooden floor, have carpet or a rug under the bed as this will trap dust for vacuuming, as dust blows off bare floors.

Curtains - ideally should be lightweight as they are easier to clean and wash.

Furniture - should be simple, clean design (avoid ornately carved furniture)

Decorations - avoid dried flowers and embossed wallpaper as they can trap dust.

Toys - mites in children's toys can be killed by washing at 60 degrees or more or leaving them in the freezer for 24 hours.

(March 2001)

Page Created: 10/2/03