Respiratory comorbidity in South African children with atopic dermatitis

Abstract

This article explores the comorbidity between AD, food allergy, aeroallergen sensitisation, asthma and allergic rhinitis in South African (SA) children. Age-dependent patterns of aeroallergen sensitisation are explored, and indoor v. outdoor aeroallergens are differentiated with regard to risk profiles for comorbid conditions. Background. Atopic dermatitis (AD) is an early and important step in the propagation of the allergic march, enhancing food and respiratory allergies via epicutaneous sensitisation to allergens. Objectives. To determine the prevalence and patterns of aeroallergen sensitisation, asthma and allergic rhinitis in South African (SA) children with AD.Methods. This was a prospective, observational study in a paediatric university hospital in Cape Town, SA. Children with moderate to severe AD, aged 6 months -10 years, were recruited randomly and investigated for food sensitisation and allergy. They were assessed for sensitisation to aeroallergens by the immuno solid-phase allergen chip test. House-dust mite DerP and DerF, dust mite Eur m, Timothy grass, Bermuda grass, tree pollen, mould (Alternaria), cat and dog sensitisation patterns were analysed. Symptoms of asthma and allergic rhinitis were elicited using a questionnaire modified from the International Study of Asthma and Allergies in Childhood study questions. Results. One hundred participants (59 black Africans and 41 of mixed ethnicity) were enrolled (median age 42 months). Of the participants, 39% had symptoms of asthma and 53% symptoms of allergic rhinitis; 89% tested positive to at least one aeroallergen, most commonly house-dust mite DerP or DerF (81%), dust mite Eur m (51%), Timothy grass (36%) and cat (35%). Asthma, allergic rhinitis and aeroallergen sensitisation all increased with increasing age, while food allergy decreased with age. Food allergy was not an independent risk factor for respiratory allergies. Children were sensitised to indoor allergens (house-dust mite, pets) from an early age, while pollen allergies increased with age. Conclusions. In this cohort of SA children with moderate to severe AD, comorbidity with respiratory allergies was high. The prevalence of respiratory allergies increased with age while food allergy decreased with age, in keeping with the pattern of the allergic march. Seasonal allergies increased with age, while house-dust mite and pet allergy peaked in younger children, in keeping with early exposure via a defective skin barrier. Early and effective restoration of the skin barrier in AD may be a target for reducing aeroallergen-related diseases.

Molecular IgE sensitization profiles of urban and rural children in South Africa

“…In a previous study in children with AD in South Africa, 66% were food sensitized, but only 40% were challenge proven to be food allergic. [13][14][15][16][17] In our cohort, cow's milk sensitization was uncommon; notably, serum albumin (Bos d 6) was recognized most frequently. There is an extensive cross-reactivity of IgE antibodies with albumins from different sources, like milk, meat, and dander.…”

“…However, our study has reported sensitization rather than allergy rates, and it is well established that not all food‐sensitized patients are truly allergic. In a previous study in children with AD in South Africa, 66% were food sensitized, but only 40% were challenge proven to be food allergic 13‐17 …”

Parental History of Atopic Diseases and Presence of Allergic Rhinitis and Asthma in Children with Atopic Dermatitis

“…Studies on children who have atopic comorbidities reported inconsistent findings. For example, in South Africa, the prevalence of allergic rhinitis in children with AD was 53% and that of asthma 39% (16). In this cohort of children (16), atopic disorders such as allergic rhinitis and asthma, as well as sensitivity to aeroallergens had an increasing tendency with advancing age.…”

“…For example, in South Africa, the prevalence of allergic rhinitis in children with AD was 53% and that of asthma 39% (16). In this cohort of children (16), atopic disorders such as allergic rhinitis and asthma, as well as sensitivity to aeroallergens had an increasing tendency with advancing age. Studies in Asian population, such as in South Korea (17), reported that the prevalence of AD and allergic rhinitis were the highest at the age of 4-6 years (10.2%).…”

“…The lowest prevalence was observed among children aged 10-13 years (1.8%). In consideration of literature data (16,17) and the prevalence of allergic rhinitis and asthma in children with AD observed in our study, it can be assumed that ethnic differences in atopic comorbidities exist, and they can be explained by different phenotypes (18).…”