Asthma and low-allergen houses
What is an allergen?
An allergen is a substance that sets off an allergic reaction. For many people with asthma, exposure to a substance to which they are allergic (the allergen) makes their asthma symptoms worse. That is, exposure to this allergen ‘triggers’ their asthma.
Common allergens that trigger asthma include house dust mite faeces, skin flakes, sweat, saliva or urine from pets — especially cats (‘cat allergen’) — and household moulds.
The asthma and allergy connection
There is a range of scientific theories about the causes of asthma, some of which link exposure to high levels of common asthma allergens in early life with the subsequent development of asthma. However, other experts place less emphasis on the importance that allergens play in determining whether or not a person will develop asthma, as it has been shown that not everyone who develops asthma has had a high level of exposure in early life to common household allergens, such as those mentioned above. Equally, not every person who is surrounded by common asthma allergens early in life will go on to develop asthma.
It is, however, agreed that the causes of asthma are complex and are not completely explained by the presence or absence of common asthma allergens during early life. Nevertheless, many people who have asthma do have a demonstrated allergy (a positive allergy blood test or skin prick test) to one or more of the common asthma allergens, and continued exposure to this allergen may be triggering their asthma symptoms.
Can a low-allergen house make a difference?
A low-allergen house aims to minimise exposure to common household asthma allergens and is based on the belief that minimising exposure to these allergens may improve asthma control and lessen asthma symptoms.
Some scientists also believe that a low-allergen house is less likely to result in babies in that house going on to develop asthma. They believe that this is particularly relevant if the parents have asthma, which indicates a genetic predisposition in that family to developing asthma.
On the other hand, the National Asthma Council states that while some people with asthma may benefit from reducing exposure to house dust mites, such strategies can be costly and difficult. It also cautions that there is not yet proof that strategies to reduce exposure to house dust mites can effectively control established asthma.
If you or your children have asthma and you are thinking about trying to avoid allergens, it is best to first consult your doctor to find out if the asthma is triggered by an allergy. Your doctor may want you to have blood tests called RASTs or undergo skin prick testing to determine this. Your doctor will also be able to advise you about whether aiming for a low-allergen house is likely to help your asthma or your child’s asthma.
Steps to take towards a low-allergen house
- Reduce dust mites and dust accumulation. Dust mites live where dust accumulates — in carpets, mattresses, bedding and pillows, soft furnishing and soft toys. They feed on the thousands of skin cells we shed each day and which become part of household dust. Steps you can take to reduce dust and dust mites include enclosing mattresses and pillows in mite-proof covers, choosing vinyl or leather covered furniture rather than fabric covers, and choosing blinds over heavy dust-collecting curtains for windows. Experts do not agree on whether switching to hard flooring improves symptoms. Aim to wash pillowcases, sheets and blankets weekly in hot water (hotter than 55°C), and regularly air doonas and other bedding in the sun (and wash in hot water every 6 weeks). Putting children’s soft toys in the freezer overnight kills dust mites but does not remove the dust mite allergen. Instead, soft toys should be washed weekly in hot water. Avoid having soft toys in the bedroom if possible.
- Increase ventilation to reduce moisture and mould, and to discourage dust mites. Dampness occurs to a certain degree in all houses simply from the effect of people breathing, cooking and showering inside. However, a lot of moisture and condensation inside encourages mould and dust mites (they prefer a moist environment), both of which can cause breathing problems. An extraction fan in your kitchen, laundry and bathroom can help, as can simple measures like placing lids on cooking pots and keeping the bathroom door closed. Clean any mould from walls with an appropriate cleaner and check for rising damp or a leaking water pipe, which may be causing long-term dampness problems. Keep the house well aired. Indoor plants may encourage moulds, so go for outdoor options.
- Reduce cat and other pet allergens. Keep pets out of the bedrooms and preferably choose pets that are suitable to be kept outdoors.
- Select appropriate heating and cooling appliances. Electric heaters are suggested for people who have asthma, as they do not create fumes or irritant particles (as can wood burning heaters). If you are sensitive to dry air, choose an electric heater that radiates warmth without using a fan. Keep air conditioning units clean. Avoid using evaporative coolers.
- Use efficient cleaning methods. Dusting surfaces using a damp or electrostatic cloth is an efficient way to pick up dust without making it (and the dust mite allergen) airborne. Use a wet or electrostatic mop on hard floors. If you have carpets, select a vacuum cleaner that has an adequate filtering system — such as a high efficiency particulate air (HEPA) filter — to help prevent allergens becoming airborne. Even with this type of system, however, vacuuming temporarily increases the amount of house dust mite allergen in the air. So if you can, get someone who is not affected to do the vacuuming, and avoid entering a room for 20 minutes after it has been vacuumed.
- Aim for a low-allergen garden. Choose plants that are pollinated by insects and birds rather than by the wind — these types of plants are more likely to be native species. Many introduced grasses and trees are culprits in triggering asthma as they produce large volumes of wind-borne pollen, e.g. rye grass. Brightly coloured ornamental flowering plants can still have a place in your garden as they tend to produce small amounts of heavier pollen that is dispersed by birds or insects. Your local asthma association can provide you with a list of suitable plants as well as those plants to avoid. On windy, high pollen days, keep the doors and windows closed and try to stay indoors. Don’t turn over the compost heap, especially in hot weather. Avoid lawn mowing if you are allergic to pollens which can be blown onto grass and forced into the air with mowing.
- Avoid irritants such as tobacco smoke inside the house. Do not smoke, and if you do, only smoke outside. Ask visitors to use the ashtrays you have placed outside for their use.
Last Reviewed: 16 May 2007