Influence of Atopic Dermatitis on Cow's Milk Allergy in Children

Background and Objectives: Cow's milk protein allergy (CMA) is the most common allergy in children. The natural history of CMA is generally favorable and the majority of children reach tolerance during childhood, even if studies show variable results. Atopic dermatitis (AD) is a complex disease from an immunological point of view. It is characterized by an impaired skin barrier function and is often the first clinical manifestation of the so-called "atopic march". The aim of our study is to evaluate, in a cohort of children with CMA, if the presence of AD in the first months of life can influence the atopic status of patients, the tolerance acquisition to cow's milk, the level of specific IgE (sIgE), and the sensitization towards food and/or inhalant allergens. Materials and Methods: We enrolled 100 children with a diagnosis of CMA referred to our Pediatric Allergology Unit, aged 1-24 months at the time of the first visit. Results: 71 children had AD and 29 did not. The mean follow-up was 5.28 years. The CMA manifestations were mainly cutaneous, especially in children with AD (91.6% vs. 51.7%; P < 0.001). Patients with AD showed higher rates of polysensitization to foods and higher levels of both total IgE and sIgE for milk, casein, wheat, peanuts, and cat dander at different ages when compared to patients without AD. We analyzed the presence of IgE sensitization for the main foods and inhalants at various ages in the two groups of patients: a statistically significant difference emerged in the two groups of patients for milk, yolk and egg white, hazelnut, peanuts, soybean, grass pollen and cat dander. Meanwhile, we did not find significant differences in terms of tolerance acquisition toward cow's milk, which was nonetheless reached around 5 years of age in 61% of patients. The level of cow's milk sIgE at the age of 5 years was significantly higher in the group of patients who did not acquire tolerance (38.38 vs. 5.22 kU/L; P < 0.0001). Conclusions: An early barrier deficiency appears to promote the development of allergic sensitization, but does not seem to influence the acquisition of tolerance.