Children under 2 years old with signs of atopic dermatitis (a.k.a. eczema) have an increased risk of developing asthma and food allergies, researchers report in JAMA Pediatrics.
In addition, they found, young children with both early-onset atopic dermatitis and a food allergy have a “very high risk” of developing asthma or allergic rhinitis.
“This finding is of great importance because atopic dermatitis and food allergies are diseases appearing often in early childhood,” wrote Caroline Roduit, MD, of the University of Zurich in Switzerland, and colleagues. “The hypothesis is that children with atopic dermatitis are more prone to develop sensitization to food allergens owing to a defect of skin barrier among those children.”
The study of 1,038 children from farm (47.7%) and other rural regions in Austria, Finland, France, Germany, and Switzerland describes four distinct clinical phenotypes for atopic dermatitis that are characterized by age of onset and the natural course of disease from birth to age 6. The end result was two early-onset phenotypes (by age 2 with persistent progression) and a late phenotype with onset after 24 months of age. The fourth phenotype included asymptomatic patients.
Atopic dermatitis affects more than 20% of children in industrialized countries, and for more than 60% of these children, the condition is apparent by 24 months. Most children outgrow atopic dermatitis, but for others, it can linger into adulthood, leading to eczema, food allergies, hay fever, and asthma. In 2015, researchers questioned whether this “atopic march” could instead be explained by different subgroups depending on disease onset and the natural course of the disease.
“Children developing those diseases in early life might require special attention for prevention strategies of respiratory allergy,” Roduit et al wrote. “It would be important to find immunologic markers for these clinical phenotypes of atopic dermatitis because it was suggested that among atopic children, there are different immunological phenotypes.”
The four phenotypes identified were:
- Early-transient, with onset by age 2, with resolution by age 4 (n = 96, 9.2%)
- Early-persistent, with onset by age 2, persisting through age 6 (n = 67; 6.5%)
- Late-onset, with onset after age 2 (n = 50; 4.8%)
- Never/infrequent phenotype (n = 825; 79.5%)
The prevalence of asthma and food allergy by age 6 was increased in children with early phenotypes manifesting by age 2, especially among children with persistent symptoms.
The number of children with the late phenotype who had asthma and food allergy “is even less than that observed for the never/infrequent phenotype. Yet, the study reports an association between the late phenotype and sensitization to food allergens at 6 years of age. This late phenotype appears to have unique molecular/immune features that are lacking in the other phenotypes, particularly in the early-persistent phenotype, which followed the atopic march as we would expect,” said Kanwaljit Brar, MD, of the Division of Pediatric Allergy & Immunology at National Jewish Health in Denver, who reviewed the study.
For children who developed atopic dermatitis after age 2, the researchers identified an association with allergic rhinitis, but not with asthma or food allergies. “The onset of atopic dermatitis after the age of 2 had a unique lack of association with other allergic diseases. There was no asthma or food allergy association with the late phenotype of atopic dermatitis compared with the other three phenotypes,” Brar said.
“This could have implications for the development of other diseases, because the early-persistent type was the phenotype with the highest association to three other allergic diseases: asthma, food allergy, and allergic rhinitis.”Full Article