The "Too Clean" Idea for Increased Allergies Given Credence By New Dishwashing Study

A new study published in the journal Pediatrics focused on "traditional cooking" and family life and instances of allergy.

The study found that families which source foods from farms, wash dishes primarily by hand and otherwise have a "traditional" household in terms of eating and cleaning habits are far less likely to have allergy sufferers in the home.

Method of food preparation and consumption linked to instances of allergic reaction

The study followed more than 1,000 Swedish children aged 7 and 8, focusing on their home life and "traditional cooking." They found that in homes which ate fermented food, bought much of their food directly from farms or hand-washed dishes had about half the instances of child allergy sufferers. The researchers found that in homes which practiced at least two of the three "traditional cooking" metrics the prevalence of allergies (food, airborne, etc) was about 19 percent versus the control group which did not do any of these practices – whose instances were 46 percent.

One of the stronger links appeared to be washing dishes by hand. A history of eczema was reported for 23 percent of children whose parents washed dishes by hand versus 38 percent in families who washed with a mechanical dishwasher.

The theory in keeping with an emerging “hygiene hypothesis,” is that a certain level of microbial exposure early in life stimulates kids’ immune systems and in some cases, might head off a hypersensitivity to allergens. The study relied on earlier studies that found that washing dishes by hand was less effective than using a mechanical dishwasher, especially in removing milk-based foods such as cheese.

The study's weakness, however, is that in homes where dishwashing is primarily by hand, socio-economic status is generally lower as well and that metric has also been associated with lower allergy risk.