Asthma and allergens

The biggest single cause of an asthma attack is the faeces of house dust mites. If you or someone in your household is asthmatic, your doctor can organise an allergy test.

There are several things you can do that may control dust mites. Whether they are relevant to you will depend on the causes of your allergy and the severity of the attacks.

• Buy allergen-barrier bedding covers which can be damp dusted. These are available from some local Asthma Societies or Air-Flow Products.
• Have a carpet-free bedroom - or even a carpet-free home - and regularly wet-mop the floors.
• Vacuum carpets and soft furnishings at least once a week with a cleaner that has a good filtration system such as HEPA, S-class or replaceable micro-filters (see below). The vacuuming probably won't remove the live mites, as they are very good at clinging to soft surfaces, but it does remove the faeces.
• Damp dust every week. Alternatively, use the vacuum cleaner's dusting brush. Avoid feather dusters, which create a cloud of dust.
• If possible, get someone else to vacuum. If not, open the windows and wear a mask, then leave the room and let the air settle for 20 to 30 minutes.
• Ensure the cleaner's dust compartment is emptied regularly (by someone else).
• Choose a cleaner with a sealable and disposable dustbag.
• Steam-cleaning carpets and upholstery may reduce the levels of dust mites for a short period, but the residual water left from the cleaning may promote fungal growth, which can also trigger asthma.

HEPA filters

Most vacuum cleaners suck up the dust and dirt along with a whole lot of air. They then filter that air through a dustbag and some other kind of filter, and blow the filtered air out a vent.

But this doesn't necessarily mean they will trap the fine particles, cat allergens and dust mites that can trigger an asthma attack. For many asthma sufferers and others with an allergy to dust mites, this can be an awful problem.

The best solution is a HEPA filter, which is designed to block small particles of dust. European manufacturers sometimes use the term S-class instead.

HEPA conforms to a worldwide standard for filters required to trap 99.97 percent of particle emissions down to 0.3 microns in size. One micron is one thousandth of a millimetre: enough to screen cigarette smoke and even bacteria.

Note that HEPA filters lose their efficiency as they clog with dust, so they need to be replaced or washed, about once a year.

Useful links

• Asthma and Respiratory Foundation: Box 1459, Wellington; Phone 04 499 4592.
• AsthmaNZ: Box 67066, Auckland; Phone 09 623 0236.
• Allergy New Zealand: Box 56-117, Auckland; Phone 0800 340 800; Email help@allergy.org.nz.
• Air Flow Products: Phone 0800 247 3569.