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Early-Life Allergen Exposure and Atopy, Asthma, and Wheeze up to 6 Years of Age

¹ Menorca Health Area, ib-salut, and Institut Universitari d'Investigacio en Ciencies de la Salut, Menorca, Spain; ² Centre for Research in Environmental Epidemiology, Institut Municipal Investigacio Medica, Barcelona, Spain; ³ Universitat Pompeu Fabra, Barcelona, Spain; ⁴ Department of Occupational and Environmental Medicine, Imperial College, London, United Kingdom; and ⁵ Environment and Pediatric Research Unit, Pediatric Service, Hospital del Mar, and Pediatric Department, Barcelona Autonoma University, Barcelona, Spain

Correspondence and requests for reprints should be addressed to Dr. Matias Torrent, ib-salut Menorca, C/ Barcelona 3, 07703-Mao (Menorca), Spain. E-mail: mtorrent{at}smen.es

Rationale: Although it is widely assumed that the incidence of childhood respiratory allergies to common aeroallergens is directly related to allergen exposure in early life, few longitudinal studies have investigated this issue, and available data are scarce and mainly limited to high-risk groups.

Objectives: To assess, in a prospective manner and in a general population, the role of early life exposures to Der p1 and Fel d1 on the inception of sensitization and asthma.

Methods: Pregnant women and their children were recruited for the Asthma Multicentre Infant Cohort Study. Overall, 1,611 newborns were initially enrolled in three cohorts in the United Kingdom and Spain. Der p1 and Fel d1 allergens were measured in household dust samples at 3 months of age for 1,474 (91.5%) participants, and skin prick tests were performed at 6 years of age on 1,182 (80.2%) participants. Wheeze and diagnosed asthma were reported in yearly questionnaires.

Measurements and Main Results: Exposure to Der p1 early in life was not related to a positive specific prick test or to asthma or persistent wheeze at 6 years of age. Fel d1 showed an association with all these outcomes (third vs. first tertile; odds ratio, 4.43 for positive specific prick test and 2.6 for diagnosed asthma).

Conclusions: Dose–response relationships between allergen exposure and sensitization or asthma may be allergen specific and nonlinear; a minimum threshold level is needed to induce sensitization, but no dose–response relationship exists above this level. The effect of a particular allergen seems to be similar on atopy and asthma inception.

Key Words: wheeze • sensitization • skin prick test • Der p1 • Fel d1

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Few longitudinal studies have investigated the role of allergen exposure early in life on the inception of atopy and asthma because data are scarce and mainly limited to high-risk groups. What This Study Adds to the Field In prospectively studied representative community samples, we found no effect of house dust mite exposure on specific sensitization or asthma and a nonlinear risk curve for Fel d1 exposure. Effects of allergen exposure approach an "all or nothing" event.

 

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