There is no relation between early indoor allergen exposure and the prevalence
of asthma, wheeze and bronchial hyper-responsiveness, according to the results
of a new study.
In a prospective birth-cohort study, Dr Susanne Lau (department of paediatric
pneumology and immunology, Humboldt university, Germany) and colleagues assessed
the relevance of mite and cat allergen exposure in the development of childhood
asthma.
Of the 1,314 newborn infants enrolled in the study from five German cities,
499 were included for being at high risk of developing asthma. Carpet dust,
as a measurement of indoor allergen exposure, was obtained at six months, 18
months and three years. Pulmonary function was tested and bronchial hyper-responsiveness
was measured at seven years of age. The researchers found that children with
sensitisation to indoor allergens showed higher bronchial responsiveness at
seven years than those without sensitisation. Although sensitisation to mite
and cat allergens was associated with indoor allergen exposure, the development
of childhood asthma was not related to cat and mite allergen exposure in the
first years of life, or to owning a cat, they say.
The authors conclude: “Once sensitisation has occurred and asthma is expressed,
persistent allergen exposure is undoubtedly associated with an increase of symptoms
and use of medication.” Allergen avoidance is important in preventing exacerbations
of asthma as part of secondary and tertiary prevention strategies but “conclusions
should be drawn with caution about the possible effects of primary prevention
measures” (Lancet 2000;356:1392).