A new study published in the journal Pediatrics has revealed that children with allergic conditions, such as eczema and hay fever, might be susceptible to developing other allergies later in life. The research examined electronic medical records of nearly 220,000 children in the US who were screened between 1999 and 2020. This study provides the most extensive evidence to date of a phenomenon known as the "allergic march," which is the natural progression of allergy-related diseases from infancy through childhood.
According to Dr. David Hill, a pediatric allergy expert at the University of Pennsylvania and one of the study's authors, if a child is diagnosed with one form of allergy, they are at a significantly higher risk of developing another form compared to the general population.
The study revealed that atopic dermatitis, also known as eczema, appeared first, affecting over 10% of children studied, typically around 4 months of age. Around 13 months old, peak onsets of anaphylactic food allergies and asthma were observed in young kids, with asthma occurring in over 1 in 5 children.
When the children reached a little over 2 years old (26 months), the researchers found high rates of acute rhinitis, or hay fever, in 19.7% of kids. By 35 months, some children would go on to develop eosinophilic esophagitis, a rare allergic condition that causes inflammation in the esophagus, marking the fifth step along the allergic march.
The study is groundbreaking as it is the first national-level research based on patient healthcare data showing the occurrence of the allergic march.
Allergic conditions can have a significant impact on children's lives, leading to issues like poor academic performance, school absenteeism, anxiety, and even eating disorders in the case of food allergies.
Traditionally, large-scale research on allergies relied on surveys sent to parents, which could lead to inaccuracies. Using data from healthcare providers' records, as done in this study, can improve accuracy.
Dr. Jonathan Bernstein, president of the American Academy of Allergy, Asthma, and Immunology, however, notes that even this approach isn't perfect and variations in how physicians classify patients and input diagnoses into medical records could still introduce errors.
The study also highlights racial disparities in allergy prevalence, indicating that Black children are more likely to have eczema and asthma, while Hispanic children have consistently low rates of food allergies. Eosinophilic esophagitis, previously believed to primarily affect White male children, was found in 40% of non-white kids.
To reduce the risk of allergies, early intervention and diagnosis are crucial. Conditions like eczema involve disruption of the outermost layer of skin, known as the epithelial barrier, which allows allergens to trigger an immune response. Early diagnosis and treatment of eczema to restore the skin barrier could potentially limit the development of other allergies along the allergic march.
Bernstein emphasizes the importance of early steps such as breastfeeding and minimizing antibiotic use in infants to promote a healthier internal microbiome, which can influence whether a child continues to progress toward an allergic phenotype.