Study population
A total of 304 children were screened, and 299 were enrolled in the
study. Of them, 269 (90%) were retained at the 1styear, and 237 (79%) were retained at the 2nd year
(Figure S1). Table 2 presents the characteristics of the study
population. The mean age in months was 13.3, and 51% of the children
were less than 12 months. Figure S2 shows the age distribution. More
boys (64.5%) than girls were enrolled. Most (86.3%) of the children
had food allergies, including to egg (77%), milk (43%), wheat (25%)
and other foods (17%). Those rates correspond with the reported
prevalences of food allergies in Japan.20 Atopic
dermatitis was diagnosed in 70.2% of the children. A history of
wheezing that was not diagnosed as asthma was found in 17.3%, and a
history of lower respiratory infection was found in 10.0%. Table 2 also
shows the prevalences of various environmental factors such as pet
keeping, presence of siblings, daycare use and passive smoking, and a
parental history of asthma and allergic rhinitis.