From the abstract of a 2006 study done in Japan:
An epidemiological study was carried out on  first-year junior high school students in Wakayama Prefecture. Analyses were performed to investigate the relationships among eating habits of fermented milk or fermented soybean foods and the presence of atopic diseases. Serum levels of total IgE values, specific IgE to house dust mite and Japanese cedar pollen in these subjects were evaluated to clarify atopic status. . . . RESULTS: Serum total IgE levels were found to be significantly lower in those subjects habitually eating yogurt and/or fermented milk drinking, in comparison with those who do not habitually eat such fermented milk foods. Subjects with habitual intake of these fermented milk foods were significantly lower in having various allergy diseases compared with those without such an eating habit. However, no difference was found on the total IgE titers and having allergy diseases between subjects with or without habitual intake of Natto, a fermented soybean food.
Note the small sample size. Contrary to some experts, it’s a good sign. It means the differences were strong enough to be significant in a relatively small sample. A review article about allergies and fermented foods.
Last January (2008) I got home from Japan and started eating miso soup so often I forgot what I used to eat. This January (2009) I went to the Fancy Food Show and became so interested in fermented foods I’m having trouble remembering what I used to blog about.
Thanks to Peter Spero.