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British Guideline on the MAnAGeMent of AsthMA
3 non-pharmacological management
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There is a common perception amongst patients and carers that there are numerous
environmental, dietary and other triggers of asthma and that avoiding these triggers will improve
asthma and reduce the requirement for pharmacotherapy. Failure to address a patient, parent or
carer’s concern about environmental triggers may compromise concordance with recommended
pharmacotherapy. Evidence that non-pharmacological management is effective can be difficult
to obtain and more well controlled intervention studies are required.
This section distinguishes:
1. primary prophylaxis - interventions introduced before the onset of disease and designed to
reduce its incidence.
2. secondary prophylaxis - interventions introduced after the onset of disease to reduce its
impact.
3.1 PriMAry ProPhylAxis
The evidence for primary interventional strategies is based predominantly on observational
studies, though some have been tested using experimental methods. Many are multifaceted and
it can be difficult to disentangle the effects of one exposure or intervention from another.
3.1.1 AEROALLERGEN AvOIDANCE
Exposure to high levels of house dust mite allergen in early life is associated with an increased
likelihood of sensitisation to house dust mite by three to seven years of age. 123 Sensitisation
to house dust mite is an important risk factor for the development of asthma 124,125 and a
few studies have suggested that high early house dust mite exposure increases the risks of
subsequent asthma. 126,127 A UK study showed that low levels of house dust mite and cat allergen
exposures in early life increased the risk of IgE sensitisation and asthma at five years, with some
attenuation at high levels of exposure, but there were significant interactions with heredity and
birth order. 128
Outcomes from intervention studies attempting to reduce exposure to house dust mites are
inconsistent. A multifaceted Canadian intervention study showed a reduced prevalence of
doctor-diagnosed asthma but no impact on other allergic diseases, positive skin prick tests or
bronchial hyper-responsiveness; 129 others have shown no effect on either allergic sensitisation or
symptoms of allergic diseases. 130 In one UK study, early results from environmental manipulation
commenced in early pregnancy and focused mainly on house dust mite avoidance, showed
reductions in some respiratory symptoms in the first year of life. 131 Subsequent results showed a
paradoxical effect with increased allergy but better lung function in the intervention group. 132
The considerable variation in the methodology used in these studies precludes the merging of
data or generation of meta-analyses.
Intensive house dust mite avoidance may reduce exposure to a range of other factors including
endotoxin. Epidemiological studies suggest that close contact with a cat or a dog in early life may
reduce the subsequent prevalence of allergy and asthma. 133,134 This has raised the question of
whether high pet allergen exposure causes high-dose immune tolerance or increases exposure
to endotoxin and other microbial products as a component of the “hygiene hypothesis”.
In the absence of consistent evidence of benefit from domestic aeroallergen avoidance it is
not possible to recommend it as a strategy for preventing childhood asthma.
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