Increasing severity of early‐onset atopic dermatitis, but not late‐onset, associates with development of aeroallergen sensitization and allergic rhinitis in childhood

Abstract Background Early exposure to allergens through a defect skin barrier has been proposed as a mechanism for inducing sensitization and development of allergic diseases. We hypothesized that early‐onset, severe atopic dermatitis (AD) is associated with development of aeroallergen sensitization and allergic rhinitis. Methods We included 368 children from the Copenhagen Prospective Studies on Asthma in Childhood 2000 (COPSAC 2000 ) at‐risk mother‐child cohort. AD was diagnosed prospectively based on Hanifin&Rajka's criteria and severity assessed using the Scoring Atopic Dermatitis (SCORAD) index. Early‐onset AD was defined as debut ≤1 year, late‐onset as debut from 1–6 years. Aeroallergen sensitization and allergic rhinitis were diagnosed at ages 6–7 and 12 years. Associations between early‐onset and late‐onset AD and allergy endpoints were calculated using general estimating equations (GEE) models to compute the overall odds ratios (OR) for both time points. Results Early‐onset AD (yes/no) and severity (SCORAD) were associated with development of aeroallergen sensitization during childhood; GEE OR = 1.68 [1.08; 2.62], p = .02 and 1.08 [1.03; 1.12], p < .001, whereas late‐onset AD showed a borderline significant association and late‐onset severity showed no association; GEE OR = 1.65 [0.92; 2.94], p = .08 and 1.01 [0.97; 1.06], p = .55. The same trend was seen for allergic rhinitis with significant association between early‐onset AD and allergic rhinitis; GEE OR = 1.56 [1.01; 2.41], p = .04 and severity; GEE OR = 1.09 [1.05; 1.13], p < .001, whereas late‐onset AD showed no association. The effects on sensitization and rhinitis of early‐onset versus late‐onset AD severity were significantly different: p ‐interaction sensitization = .03 and p ‐interaction rhinitis < .01. Conclusion Increasing severity of early‐onset AD, but not late‐onset AD, associates with aeroallergen sensitization and allergic rhinitis later in childhood.