Overweight is associated with allergy in school children of Taiwan and Vietnam but not Japan.

We collected information concerning diagnosed allergy from 2027 school children in Japan, Taiwan and Vietnam. Children were classified according to the age and sex-specific body mass index (BMI) per-age as indicator of weight status. Logistic regression was performed to examine the relationship between percentiles of BMI-per-age and allergy. Compared with children at the lowest percentile group Taiwanese children at > 85th percentile group showed a tendency toward higher risk of allergy (OR = 1.79, 95% CI 0.98 to 3.27; p = 0.060). When children with rhino-conjunctivitis were excluded from the analysis the association reached statistical significance (OR = 2.89, 95% CI 1.08 to 7.75; p = 0.035). Vietnamese children at > 85th percentile group showed a significantly higher risk of allergy (OR = 2.34, 95% CI 1.06 to 5.17; p = 0.035). This association was not observed when children with atopic dermatitis or food allergy were excluded from the analysis, although a tendency toward increased risk of allergy at BMI-per-age > 85th percentile remained. Our study sample of Japanese school children showed no association between being overweight and allergy.