The development of allergic multimorbidity in childhood: patterns, mechanisms, and prediction

Eczema, allergic rhinitis, and asthma are traditionally considered as atopic (or allergic) diseases. They are complex diseases and caused by a variety of different mechanisms. The “Atopic March” is usually interpreted as the sequential development of symptoms from eczema in infancy to asthma, and then allergic rhinitis in later childhood. The origins of this framework arose from epidemiological studies based on point prevalence from cross-sectional data at the population level. However, the atopic march describes a trajectory that exists at the individual level. Although attempts have been made to “stop the march” or prevent the onset of other atopic illnesses in those with eczema, such studies have been unsuccessful, and this may because of heterogeneity in the etiology and pathophysiology underlying the diseases.
The availability of birth cohort data combined with machine learning has provided new ways to capture different patterns of allergic diseases within individual patients. Recent studies have shown that a linear progression of symptoms does not capture the number and complexity of allergic phenotypes. Less is known about how different patterns of allergic disease are influenced by socioeconomic circumstances and ethnic background, in part due to a lack of available data with repeated measures at the individual level. Consequently, the extent of social and ethnic inequalities in different patterns of allergic disease and the mediators driving any inequalities also remains unknown. Identifying these in historically under-studied groups would enable us to inform stratified targeted interventions to reduce disparities in patient outcomes.