How can you avoid allergens?

The most common allergic triggers of asthma are house dust mite, pets, pollen and moulds.

Even though complete allergen avoidance will not cure asthma, reduced exposure to your allergen triggers may lead to improved control of your asthma and reduce your need for medication.

House dust mite

House dust mites:

•  are the most common allergen triggers for asthma in Australia

•  are microscopic creatures that feed off human skin scales

•  live in soft furnishings such as beds, bedding, carpets, upholstered furniture, soft toys and clothing

•  thrive in temperate and humid climates such as coastal Australia

•  are mostly found in domestic houses rather than public places

•  are not usually in the air and only become airborne during and after dust-raising activities such as vacuuming and dusting.

How can house dust mite levels be reduced?

If you are allergic to house dust mites you may be advised to take measures (see pages 7-10) to:

•  kill house dust mites

•  remove the allergen they produce

•  reduce areas where they live and breed.

The greatest exposure to house dust mites is from your bedding. Therefore the avoidance measures on the following pages focus on the bedroom.

House dust mite avoidance     

Bedding

A combination of the following measures (1-4) has been shown to benefit asthma control.

1 Cover mattress, pillow and quilt with dust mite resistant covers. The covers must be washed every 2 months. Some health funds may provide a rebate for the purchase of these items. If covers are not available, wash blankets and non-encased washable doonas every 3 months, using the method described below for sheets.

2 Wash sheets and pillow cases weekly in water hotter than 55˚C. This will kill mites and wash away the allergen they produce. If you cannot wash in hot water, use a commercial product containing essential oils such as tea tree or eucalyptus oils, formulated to kill dust mites in cold water.

If washing normally, hot tumble drying of washed items for 10 minutes after they are dry will kill mites. Dry cleaning is not as effective as it will kill house dust mites but won’t remove the allergen they produce.

3 Remove sheepskin or woollen underlays.

4 Remove all soft toys from the bed and bedroom. Replace them with wooden or plastic toys which can be washed. If a soft toy is allowed it should be washed weekly using the method described for sheets. It should be noted that freezing soft toys overnight kills mites but doesn’t remove allergen.

Ideal bedroom

Other Measures

•  Damp dust or use electrostatic cloths to clean hard surfaces (including hard floors) weekly.

•  Vacuum carpets weekly
Vacuuming increases the amount of house dust mite allergen in the air for up to 20 minutes. So, if possible, ask someone else to do the vacuuming and wait for 20 minutes before re-entering the room. High efficiency particulate air (HEPA) filter vacuum cleaners may remove more allergen than other vacuum cleaners. However, they still increase the amount of dust mite allergen in the air.

•  Consider replacing carpets with hard floors such as wood, tiles, linoleum, concrete, where practical and affordable. Carpets can contain large amounts of house dust mite and animal allergens which cannot be completely removed by vacuuming. Although this will reduce allergen exposure, the benefits on asthma control are yet to be proven.

•  Reduce humidity – have a dry and well ventilated house, adequate floor and wall insulation and avoid evaporative coolers.

•  Windows – venetian blinds or flat blinds are easier to clean than heavy curtains. Washable curtains or external shutters are other options.

•  Consider house dust mite avoidance measures when building a new home.

The most important measures House dust mite avoidance measures should focus on the bedroom and require an ongoing commitment. House dust mite levels can only be reduced by using a combination of: •  bedding covers •  regular washing •  reducing places where house dust mites can live and breed.

Products that are not recommended

•  Sprays (acaracides) – there is limited information on their effectiveness and safety.

•  Domestic dehumidifiers have not been shown to benefit asthma control.

•  Air cleaning devices – house dust mite allergen is only in the air for a short time during and after dust-raising activities such as vacuuming and dusting.

Figure 2  House dust mite (magnified)