Coincidence of pollen season with the first fetal trimester together with early pet exposure is associated with sensitisation to cat and dog allergens in early childhood: a Finnish population-based study

Abstract

Background

Children whose 11^th fetal week falls in pollen season (spring) reportedly have an increased risk of sensitisation to food allergens. No such finding has been reported for pet allergens.

Objective

The aim of the study was to 1) evaluate the incidence of pet (dog and cat) sensitisation according to the season of the 11^th fetal week and 2) whether the association between pet exposure and respective sensitisation is modified by the coincidence of the 11^th fetal week with pollen season.

Methods

The study population comprised all children (born between 2001 and 2006) in the province of South Karelia, Finland (N=5920). Their data of IgE and skin prick tests to pet allergens (N=538) were collected from patient records and linked with questionnaire data on pet exposure.

Results

The seasonal incidence peak of cat sensitisation was observed in children whose 11^th fetal week occurred in June (7.4%) and that of dog sensitisation in April (3.8%) and June (4.7%). The relative rate (RR) for cat sensitisation was 2.92 (95% CI 1.40-6.08) in children with cat exposure alone, 8.53 (4.07−17.86) in children with cat and fetal pollen exposures, and 0.61 (0.20−1.83) in children exposed to pollen alone, compared with children without these exposures. The respective RRs for dog sensitisation were 2.17 (1.13-4.19), 4.40 (2.19−8.83) and 1.65 (0.77−3.53).

Conclusions and clinical relevance

Coincidence of the first fetal trimester with pollen season strengthens the association between pet exposure and respective sensitisation. Pollen exposure at early pregnancy may deviate immune system towards Th2 type reactivity promoting development of specific allergy in case allergen exposure occurred. Therefore, primary prevention of allergic diseases may need to begin during early pregnancy.

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