Study casts doubt on allergens link to asthma

REDUCING levels of household allergens, such as cat fur and dust mites, is unlikely to have a major impact on cutting asthma and allergies in children, according to a new study.

Researchers in the last 20 years have claimed the risk of childhood respiratory allergies is linked to how strongly children are exposed to allergens in early life. But the latest research, published in the journal Thorax, casts doubt on how much influence early exposure to such allergens actually has on the risks of youngsters developing asthma or allergies.

The researchers, from the Imperial College School of Medicine at the National Heart and Lung Institute in London, based their conclusions on a study of 625 children in Ashford, Kent.

These youngsters were monitored from birth until 5½, with 552 eventually tested for sensitisation to house dust mites, cat fur and grass pollens.

The mothers were interviewed every year to find out whether their children had suffering wheezing in the past 12 months.

The researchers, led by Dr Paul Cullinan, also collected house dust samples from the families’ living room floors when the youngsters were eight-weeks-old.

They found that 10% of the children were sensitised to dust mites or cat fur by 5½, and 7% had suffered associated wheezing in the last year.

However, they found no significant links between the levels of exposure to household allergens, measured in their dust samples, and sensitisation or frequency of wheezing. Both sensitisation and wheezing occurred in response to very low allergen levels.

Children were also significantly more likely to suffer from these conditions if their father had an inherited susceptibility to an allergy or the child was a firstborn.

“If exposure thresholds for sensitisation or asthma exist, then they appear to be exceedingly low,” they said.

“They (the findings) also make it improbable that reductions in domestic allergen exposure alone will have a major impact in reducing the incidence of these diseases in childhood.

“Measures that cut rather than eliminate exposure may even give rise to arise in rates of sensitisation.”