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British Guideline on the MAnAGeMent of AsthMA
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Measures to decrease house dust mites have been shown to reduce numbers of house dust
mites, but have not been shown to have an effect on asthma severity.
; Families with evidence of house dust mite allergy and who wish to try mite avoidance
might consider the following:
complete barrier bed-covering systems
removal of carpets
removal of soft toys from bed
high temperature washing of bed linen
acaricides to soft furnishings
good ventilation with or without dehumidification.
3.2.2 OTHER ALLERGENS
Animal allergens, particularly from cat and dog, are potent provokers of asthma symptoms.
The reported effects of removal of pets from homes are paradoxical, with either no benefit
for asthma 179,180 or a potential for continued high exposure to induce a degree of tolerance. 181
In homes where there is no cat but still detectable cat allergen, there may be a benefit from
introducing additional avoidance measures such as air filters and high efficiency vacuum
cleaners for cat allergic patients. 182,183
Although fungal exposure has been strongly associated with hospitalisation and increased
mortality in asthma, no controlled trials have addressed the efficacy of reduction of fungal
exposure in relation to control of asthma. Cockroach allergy is not a common problem in the UK
and studies of attempts to avoid this allergen elsewhere have produced conflicting results. 184
Studies of individual aeroallergen avoidance strategies show that single interventions have
limited or no benefit. A multi faceted approach is more likely to be effective if it addresses all
the indoor asthma triggers. Such approaches may even be cost effective. 185 A strategy with a
potential impact on mites, mould allergens and indoor pollutants is the use of a mechanical
ventilation system to reduce humidity and increase indoor air exchange. The only trial that
has assessed this in a controlled fashion failed to demonstrate any significant effects, but the
numbers involved were small. 120 A systematic review of this topic concluded that more research
is required. 186
3.3 other environMentAl fACtors
3.3.1 SMOKING
Direct or passive exposure to cigarette smoke adversely affects quality of life, lung function,
need for rescue medications for acute episodes of asthma and long term control with inhaled
steroids. 187-190
There are very few trials which have assessed smoking cessation in relation to asthma control.
Two studies have demonstrated decreases in childhood asthma severity when parents were
able to stop smoking. 191,192 One study in adults with asthma suggested that smoking cessation
improved asthma-specific quality of life, symptoms and drug requirements. 193 Intervention to
reduce smoking has had disappointing outcomes. 194,195 It is likely that more intensive intervention
will be required to achieve meaningful outcomes. 196
Uptake of smoking in teenagers increases the risks of persisting asthma. One study showed
a doubling of risk for the development of asthma over six years in 14 year old children who
started to smoke 197 (see section 4.2.4 for effect of smoking on treatment).
C Parents with asthma should be advised about the dangers of smoking to themselves
and their children with asthma and offered appropriate support to stop smoking.
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