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J Allergy Clin Immunol. 2011 Oct;128(4):880-885.e4. doi: 10.1016/j.jaci.2011.06.039. Epub 2011 Aug 5.

Effect of prenatal indoor pet exposure on the trajectory of total IgE levels in early childhood.

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Department of Public Health Sciences, Henry Ford Hospital, Detroit, MI 48202, USA.



The presence of pets in a home during the prenatal period and during early infancy has been associated with a lower prevalence of allergic sensitization and total IgE levels in middle childhood. No studies have examined the effect of pet exposure in a population-based cohort by using multiple early-life measures of serum total IgE.


We sought to examine within-individual longitudinal trends in total IgE levels during early childhood and assess the effect of indoor prenatal pet exposure on those trends. Also, we sought to use a statistical method that was flexible enough to allow and account for unequally spaced study contacts and missing data.


Using the population-based Wayne County Health, Environment, Allergy and Asthma Longitudinal Study birth cohort (62% African American), we analyzed 1187 infants with 1 to 4 measurements of total IgE collected from birth to 2 years of age. Effects of pet exposure on the shape and trajectory of IgE levels were assessed by using a multilevel longitudinal model, accommodating repeated measures, missing data, and the precise time points of data collection.


The best-fit shape to the trajectory of IgE levels was nonlinear, with an accelerated increase before 6 months. Total IgE levels were lower across the entire early-life period when there was prenatal indoor pet exposure (P < .001). This effect was statistically significantly stronger in children delivered by means of cesarean section versus those delivered vaginally (P < .001 and P < .06, respectively) and in those born to non-African American (P < .001) versus African American (P < .3) mothers.


Pet exposure and delivery mode might be markers of infant exposure to distinct microbiomes. The effect of exposures might vary by race, suggesting a differential effect by ancestry.

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