Supplementary Material for: A Population-Based Study of Fish Allergy in the Philippines, Singapore and Thailand

Background: Fish allergy is the third most common food allergy after milk and egg in parts of Europe, but there is little data about prevalence in South East Asia where it is an important part of regular diets. Objective: We aimed to obtain an estimate of the population prevalence of fish allergy among older children in the Philippines, Singapore and Thailand. Methods: The population prevalence of fish allergy in 14- to 16-year-old children in the 3 countries was evaluated using a structured written questionnaire which was distributed to students of randomly selected secondary schools. An extended questionnaire to determine convincing fish allergy on the basis of typical clinical manifestations within 2 h of ingestion was administered to those with positive responses. Results: From acohort of 25,842 students, responses were 81.1% in the Philippines (n = 11,434), 67.9% in Singapore (n = 6,498) and 80.2% (n = 2,034) in Thailand. Using criteria for convincing food allergy, fish allergy was much higher in the Philippines [2.29%, 95% confidence interval (CI) 2.02–2.56] than in Singapore (0.26%, 95% CI 0.14–0.79) and Thailand (0.29%, 95% CI 0.06–0.52). Weighted multiple logistic regression analyses showed that compared to the Philippines, prevalence rates were lower in Singapore [odds ratio (OR) 0.40, 95% CI 0.27–0.60, p < 0.0001] and Thailand (OR 0.13, 95% CI 0.05–0.33, p < 0.0001). Females were more likely to have fish allergy compared to males for all children combined (OR 1.32, 95% CI 1.11–1.58, p = 0.002). Most allergies appeared mild, as only 28% of cases sought medical consultation at the time of the reaction and 31.2% of cases reported continued exposure despite allergic symptoms. Conclusion: Fish allergy in late childhood is more common in the Philippines compared to Singapore and Thailand. Differences in food processing, dietary habits and other cultural practices might be important risk factors for the development of fish allergy in these populations.