Trends in food allergy among Hong Kong preschoolers: Findings from 2006, 2013, and 2020 surveys.

Background: Food allergy (FA) significantly impacts quality of life and public health, but data on prevalence trends in Asia remain limited. This study investigated trends in FA prevalence and related allergic conditions among preschool Chinese children over a 15-year period.

Methodology: Cross-sectional surveys were conducted in 2006, 2013, and 2020, targeting nurseries, preschool, and daycare centers across Hong Kong. Data were collected using a standardized, parent-reported questionnaire adapted from the International Study of Asthma and Allergy in Childhood (ISAAC), assessing the prevalence of perceived (parent-reported) and probable (doctor-diagnosed) FA.

Results: A total of 11,537 Chinese children aged 2-7 years from 70 schools were surveyed across the three time points, with response rates ranging from 60% to 80%. The prevalence of perceived FA increased from 6.1% (95% CI, 5.4%-6.9%) in 2006 to 9.5% (95% CI, 8.6%-10.5%) in 2013 but declined to 8.5% (95% CI, 7.7%-9.3%) in 2020. Probable FA prevalence showed nonsignificant change, from 4.4% (95% CI, 3.8%-5.1%) in 2006 to 5.1% (95% CI, 4.5%-5.8%) in 2020. Longitudinal analysis revealed significant sustained increases in egg (doubled to 1.86%), peanut (nearly tripled to 1.52%), tree nut (five-fold increase to 0.68%), and shellfish allergic reactions (increased to 1.99%). Trends in atopic comorbidities included declines in asthma and wheezing, fluctuations in rhinitis, and an increase in eczema.

Conclusions: Perceived FA increased over time, while probable FA remained stable, with shifts in allergens. Further research should explore this divergence and focus on enhancing allergy services and improving public awareness.