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.

Keywords: Africa; allergy; egg; ethnicity; food allergy; food sensitization; peanut; prevalence; rural; skin prick test; urban.