The prevalence and patterns of IgE-mediated food allergy and sensitisation in South African children with atopic dermatitis

Includes bibliographical references.Background: The prevalence of food allergy in South Africa is unknown, but previously thought to be low, particularly in black South Africans. We hypothesised that food allergies would be low in Xhosa patients, even those at increased risk of food allergy such as children with atopic dermatitis (AD). This study aimed to determine the prevalence of, patterns and risk factors for, IgE-mediated food allergy in South African children with moderate to severe AD. It is the first food allergy prevalence study in South Africa to utilise controlled food challenges and component analysis, and is unique for its comparison of food allergy patterns between ethnic groups in the same geographical area. Methodology: This was a prospective, observational study in a paediatric university hospital in Cape Town. Children with moderate to severe AD, aged 6 months to 10 years, were randomly recruited from the dermatology clinic. They were assessed for sensitisation and allergy by questionnaire, skin prick tests (SPT), Immuno Solid Phase Allergen Chip (ISAC) test and incremental food challenges. Sensitised patients were also tested for specific IgE by ImmunoCAP test. Results: One hundred participants (59 black Africans and 41 of mixed race) were enrolled, median age 42 months. There were high overall rates of food sensitisation (66%) and food allergy (40%). Egg (25%) and peanut (24%) were the most common allergies. Black participants had comparable sensitisation (69% vs 61%) but lower allergy rates (34% vs 46%) than mixed race participants. This was especially evident for peanut allergy (15% vs 37%, p=0.01). Early onset AD (< 6 months), severe eczema, and young age < 2 years were significant risk factors for food allergy. The ISAC test was less sensitive than SPT and ImmunoCAP tests. Only 42% of cases of perceived food allergy were confirmed as true food allergy