Rural and urban food allergy prevalence from the South African Food Allergy (SAFFA) study

Abstract

Background: Food sensitization and challenge‐proved food allergy (FA) have not been compared in urban and rural settings. Objective: We sought to determine and compare the prevalence of food sensitization and challenge‐proved IgE‐mediated FA in urban and rural South African toddlers aged 12 to 36 months. Methods: This cross‐sectional study of unselected children included 1185 participants in urban Cape Town and 398 in the rural Eastern Cape. All participants completed a questionnaire and underwent skin prick tests (SPTs) to egg, peanut, cow s milk, fish, soya, wheat, and hazelnut. Participants with SPT responses of 1 mm or greater to 1 or more foods and not tolerant on history underwent an open oral food challenge. Result: The prevalence of FA was 2.5% (95% CI, 1.6% to 3.3%) in urban children, most commonly to raw egg white (1.9%), followed by cooked egg (0.8%), peanut (0.8%), cow s milk (0.1%), and fish (0.1%). Urban sensitization (SPT response ≥1 mm) to any food was 11.4% (95% CI, 9.6% to 13.3%) and 9.0% (95% CI, 7.5% to 10.8%) at an SPT response of 3 mm or greater. Sensitization in rural cohorts was significantly lower than in the urban cohort (1‐mm SPT response, 4.5% [95% CI, 2.5% to 6.6%]; 3‐mm SPT response, 2.8% [95% CI, 1.4% to 4.9%]; P < .01). In the rural black African cohort 0.5% (95% CI, 0.1% to 1.8%) of children had food allergy, all to egg. This is significantly lower than the prevalence of the urban cohort overall (2.5%) and urban black African participants (2.9%; 95% CI, 1.5% to 4.3%; P = .006). Conclusion: FA prevalence in Cape Town is comparable with rates in industrialized middle‐income countries and is significantly greater than in rural areas. Further analysis will describe and compare environmental exposures and other risk factors in this cohort.