Allergy in Children in Hand Versus Machine Dishwashing

Abstract

To investigate whether dishwashing methods by variably altering microbial exposure could impact the risk of allergy development.Children (N = 1029) 7 to 8 years of age from Kiruna and Mölndal, 2 cities in Sweden.Questionnaire-based study, including questions on asthma, eczema, and rhinoconjunctivitis taken from the International Study of Asthma and Allergies in Childhood questionnaire.Hand dishwashing was associated with a reduced risk of allergic disease development (multivariate: odds ratio 0.57; 95% confidence interval: 0.37–0.85). This risk was further reduced in a dose-dependent manner if the children were also served fermented food and if the family bought food directly from farms.Allergic diseases are less common in children whose families use hand dishwashing versus machine dishwashing. This phenomenon may be due to increased microbial exposure with a less efficient dishwashing method leading to more induction of allergen tolerance.Over the past 20 years, the hygiene hypothesis has been proposed as 1 reason for the rising prevalence of allergic diseases in the later part of the 20th century. The hypothesis proposes that microbial exposure early in life stimulates the immune system in a manner that helps induce allergen tolerance. Several studies including those by von Mutius and others in farming communities lend credence to this hypothesis. The goal of this study was to also see whether simple variations in daily life exposure patterns (eg, due to varied dishwashing practices) might also play a role. The authors do point out that this was an observational study, and as such the observed trend is not necessarily causal; despite multivariate analysis, the outcome could also be due to associated lifestyle factors (eg, overcrowded housing, low socioeconomic status, immigration status) where hand dishwashing may simply be more common.