Pre- and early postnatal farm exposure was associated with reduced incidence of atopic dermatitis (AD) in infants, according to study data published in the Journal of Allergy and Clinical Immunology.

In this prospective Wisconsin Infant Study Cohort, the effect of gestational and early-life (first 2 months) exposure to poultry, pig, feed grain, and other animal species on the occurrence of AD was examined in children living in rural Wisconsin, from birth to 24 months. Mothers were asked to complete questionnaires to evaluate farming and other environmental exposures during pregnancy at 2, 9, and 24 months; other questionnaires determined clinical outcomes in offspring, including a diagnosis of AD delivered by a healthcare provider, as well as overall health, at 2 and 6 months of age, and every 3 months thereafter.

Participants were classified as “farm” families if they were living on or within 0.125 mile of a farm, working on a farm, or had a household member who worked on a farm. AD incidence was estimated using the Kaplan-Meier method, and was compared in farm and non-farm families using the log-rank test. Longitudinal AD prevalence was calculated using general estimating equations.

The study cohort comprised 104 farm families and 122 non-farm families. Median follow-up time was 24 months (range, 6-48 months). Sociodemographic characteristics were similar in the groups, although a smaller percentage of farm vs non-farm children were girls (43% vs 58%, respectively; P =.03). Within the farm cohort, 80% of mothers lived and worked on farms, and 16% worked on farms but lived elsewhere.


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During pregnancy, regular exposure to cattle, poultry, pigs, and goats were reported by 66%, 25%, 10%, and 7% of farm mothers, respectively. Further, 76%, 66%, 63%, and 58% reported regular contact with hay, feed grain, straw, and silage, respectively, during pregnancy.

The incidence of AD was reduced in children in the farm vs non-farm group, particularly, in the second half of the first year of life (P =.03). Farm exposure was also associated with reduced cumulative prevalence of AD during the first 2 years of life (P =.002). Within the farm cohort, rates of AD were inversely associated with prenatal exposure to: pigs (4% vs 25%; P =.01), poultry (3% vs 28%; P <01), and feed grain (13% vs 34%; P =.02). AD rate was inversely associated with the number of animal species mothers were exposed to during pregnancy. Specifically, AD rates were 43%, 31%, 16%, and 6% for farm children with prenatal exposure to 0, 1 to 2, 3 to 4, and 5 to 6 animal species, respectively.

The primary study limitation is the use of parental report vs medical records for the determination of a diagnosis of AD. Farm families also have lower levels of healthcare utilization, which may have led to underreporting of AD diagnoses.

These data suggest that farm exposure during prenatal and early life may reduce the risk for AD in children. “Given the association between early onset AD and allergic outcomes such as food allergy and asthma, identification of farm-related microbiota or other exposures that positively influence early immunobiology and reduce AD development could lead to future preventative strategies for multiple atopic diseases,” noted the study authors.

Reference

Steiman CA, Evans MD, Lee KE, et al. Patterns of farm exposure are associated with reduced incidence of atopic dermatitis in early life [published online July 7, 2020]. J Allergy Clin Immunol. doi: 10.1016/j.jaci.2020.06.025

This article originally appeared on Dermatology Advisor