Early allergen exposure, skin prick responses, and atopic wheeze at age 5 in English children: a cohort study
- Department of Occupational and Environmental Medicine, Imperial College School of Medicine at the National Heart and Lung Institute, London, UK
- Correspondence to:
Dr P Cullinan
Department of Occupational and Environmental Medicine, Imperial College School of Medicine at the National Heart and Lung Institute, Manresa Road, London SW3 6LR, UK;
- Received 5 December 2003
- Accepted 12 May 2004
Background: For many years it has been assumed that the risk of childhood respiratory allergies is related to allergen exposures in early life. There are, however, few prospective data in support. We aimed to examine this relationship in a representative cohort of children born in Ashford, Kent (UK).
Methods: 625 children (94% of those eligible) were followed from birth to the age of 5.5 years at which time 552 underwent skin prick testing to extracts of house dust mite and cat fur allergens. Maternal reports of wheeze in the last year were collected by interview. These outcomes were related to individual domestic concentrations of Der p 1 and Fel d I allergens estimated from dust collection at the age of 8 weeks.
Results: 10% of children were sensitised to house dust mite or cat at age 5.5 years; 7% had atopic wheeze. No significant relationships between allergen exposure and either sensitisation or wheeze were found but, on examination, the exposure-response relationships for both allergens and for each outcome rose steeply at low levels of exposure and were attenuated at high levels of exposure. These patterns were modified by paternal atopy and by birth order.
Conclusions: There are no linear relationships between early allergen exposure and the induction of childhood respiratory allergy; rather, the risks of IgE sensitisation and asthma rise at very low levels of exposure and are attenuated thereafter. These patterns are influenced by parental atopy and birth order. These findings suggest important gene-environment interactions in the development of atopy and asthma and imply that reductions in domestic allergen exposure alone are unlikely to have a major impact in decreasing the incidence of these diseases in childhood.
This study was funded by the Colt Foundation.
PC and ANT devised the study. It was supervised by PC and JH. SM, CW and PM collected all the data which were jointly analysed by SMc and JH. PC and SMc wrote the manuscript. All the authors had access to all the data and all hold responsibility for the decision to submit this manuscript.