A kitchen appliance that many consider essential is a dishwasher. After all, who would choose to slave over a hot sinkful of dirty dishes like grandmother had to do? However, a new study might cause parents of young children to revert that unpleasant task. It found that hand washing of dishes actually reduced the risk of childhood allergies. The findings were published in the journal Pediatrics by Swedish researchers.
The study authors point to the hygiene hypothesis as the reasoning behind hand washing. It specifies that exposure to microbes (e.g., bacteria, viruses, and fungi) during early life increases immunologic tolerance via stimulation of the immune system; thus, reducing the risk of allergy development. They explain that several common lifestyle factors and household practices, such as dishwashing methods, may increase microbial exposure. Therefore, the goal of the study was to investigate whether such lifestyle factors are associated with allergy occurrence.
For the study, the researchers issued a questionnaire, the International Study of Asthma and Allergies in Childhood (ISAAC), to 1029 children aged seven to eight years who resided in Kiruna, in the north of Sweden, and Mölndal, in the Gothenburg area on the southwest coast of Sweden. Questions regarding asthma, eczema, and rhinoconjunctivitis (nasal congestion, runny nose, post-nasal drip, sneezing, red eyes (conjunctivitis), and/or itching of the nose or eyes) were reviewed from ISAAC.
The investigators found that hand dishwashing was linked with a reduced risk of allergic disease development (43% decreased risk). The risk was further decreased in a dose-response manner if the children were also served fermented food and if the family bought food directly from farms.
The authors concluded that, in families who use hand dishwashing, allergic diseases in children are less common than in children from families who use machine dishwashing. They theorized that a less-efficient dishwashing method may encourage tolerance via increased exposure to microbes.
