THORAX

[Early allergen exposure, skin prick responses, and atopic wheeze at age 5 in English children: a cohort study Thorax 2004; 59: 855-61]

Newswise — Cutting levels of household allergens, such as cat dander and dust mite, is unlikely to have much impact on the subsequent development of childhood asthma and respiratory allergies, suggests research in Thorax.

The finding undermines the long held belief that the intensity of early life exposure to allergens directly influences the risk of developing childhood respiratory allergies and asthma, suggest the authors from the National Heart and Lung Institute, London.

They base their conclusions on 625 children in one town in southern England. They were monitored from birth until the age of 5∏ years, when 552 of them were tested for sensitisation to house dust mite, cat fur, and grass pollens.

Their mothers were also interviewed annually about whether their children had had any episodes of wheezing in the preceding 12 months. Allergen levels had been measured in house dust samples from the living room floor when the children were 8 weeks old.

One in 10 of the children was sensitised to house dust mite or cat fur by the age of 5∏, and one in 14 had associated wheezing in the preceding year.

But no significant links were found between the levels of early life exposure to household allergens and either sensitisation or frequency of wheezing.

Both sensitisation and wheezing occurred in response to very low allergen levels, and they were significantly more likely if the father had an inherited susceptibility to allergy or the child was a firstborn.

"If exposure thresholds for sensitisation or asthma exist, then they appear to be exceedingly low," say the authors. "[Our findings] imply important and previously unrecognised gene-environment interactions in the development of atopy and associated asthma," they add.

The authors also suggest that their findings "make it improbable that reductions in domestic allergen exposures alone will have a major impact in reducing the incidence of these diseases in childhood." In fact, they suggest that so doing might actually increase rates of sensitisation.

Click here to view full paper:http://press.psprings.co.uk/thx/october/855_tx19877.pdfClick here to view accompanying editorial (item 4 on PDF):http://press.psprings.co.uk/thx/october/821_editorials.pdf

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