The study team explored the association between a number of lifestyle factors and household practices, including use of different dishwashing methods, and the prevalence of allergy in 1,029 children aged seven to eight years.
The study used questions on asthma, eczema and rhinoconjunctivitis from the International Study of Asthma and Allergies in Childhood questionnaire.
Washing dishes by hand was associated with a reduced risk of allergic disease development in children compared with machine dishwashing (multivariate analysis, OR 0.57; 95% CI 0.37-0.85).
This risk was found to be further reduced in a dose-response pattern in children who ate fermented food such as sauerkraut and in those whose families bought food such as eggs, meat or unpasteurised milk directly from farms.
The authors propose that these lifestyle factors expose family members to higher levels of bacteria and reduce allergy development through immune stimulation in early life.
Hesselmar B, Hicke-Roberts A, Wennergren G. Pediatrics February 23, 2015. doi: 10.1542/peds.2014-2968