The hygiene hypothesis stipulates that microbial exposure during early life induces immunologic tolerance via immune stimulation, and hence reduces the risk of allergy development. Several common lifestyle factors and household practices, such as dishwashing methods, may increase microbial exposure. The aim of this study was to investigate if such lifestyle factors are associated with allergy prevalence.
Questionnaire-based study of 1029 children aged 7 to 8 years from Kiruna, in the north of Sweden, and Mölndal, in the Gothenburg area on the southwest coast of Sweden. Questions on asthma, eczema, and rhinoconjunctivitis were 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 analysis, odds ratio 0.57; 95% confidence interval: 0.37–0.85). The risk was further reduced in a dose-response pattern if the children were also served fermented food and if the family bought food directly from farms.
In families who use hand dishwashing, allergic diseases in children are less common than in children from families who use machine dishwashing. We speculate that a less-efficient dishwashing method may induce tolerance via increased microbial exposure.
Comments
Allergy in Children in Hand Versus Machine Dishwashing
Hesselmar et al studied the putative association between organ manifestations of allergy and the style of dishwashing in a cross- sectional design. Indeed, as the authors remind, this study design does not allow for causative relationships to be established. However, the authors did not assume that the familial sharing of atopy, which commonly manifests as rhinosinusitis, eczema, asthma and food allergies, can lead atopic parents to avoid dishwashing by hand due to its potential of increasing severity of cutaneous symptoms, namely skin xerosis. Therefore, in order to discard the effect of dishwashing as a confounding factor, the signs and symptoms of eczema in parents must also be acknowledged.
Conflict of Interest:
None declared