A recent study published in BioMed Central Pediatrics (August 2016) reports that young children diagnosed with food allergy are at increased risk of also developing respiratory allergies during the first five years of life. This finding comes from reviewing the electronic medical records of children who received care from the Children’s Hospital of Philadelphia (CHOP) clinical network. Previous studies have suggested a similar association between food allergies and other allergic conditions, but those studies were smaller, less comprehensive, or based on participant reporting.
The study investigated two groups of records: a smaller birth cohort and a larger cross-sectional cohort. The birth cohort included nearly 30,000 patient records that were established shortly after birth (age < 1 month) and continued to age 5 years. These records were used to calculate the incidence of allergic conditions – the number of new cases in a given period, divided by the population.
The cross-sectional cohort contained 333,000 records from pediatric patients ages 0 to 17. Data from these records were used to determine the prevalence of allergic conditions – the number of cases at a given point in time, divided by the population.
Within the birth cohort, 8.2 percent of patients were diagnosed with one or more food allergies by age 5. During the same period of life, 22.4 percent received a diagnosis of asthma and 17.2 percent were diagnosed with rhinitis (inflammation of the membranes that line the nose).
The likelihood of a new asthma or rhinitis diagnosis was greater in children with food allergies than in the birth cohort as a whole. By their fifth birthday, 35 percent of the children with food allergy had also developed asthma. Likewise, 35 percent of the food-allergic children went on to develop rhinitis by age 5. The odds of developing asthma or rhinitis in the first five years of life were more than two times greater for food allergy patients than for patients who did not have food allergy. Children who developed asthma or rhinitis prior to developing food allergy were not included in this analysis.
Allergy to peanut, milk or egg had a significant effect in predisposing infants and preschoolers to respiratory allergies. Young children with multiple food allergies were at greater risk of developing asthma or rhinitis than were children with a single food allergy.
Within the cross-sectional cohort, the prevalence of food allergy was 6.7 percent across all ages, while the prevalence of asthma and rhinitis was 21.8 percent and 19.9 percent, respectively. Rates of food allergy and rhinitis reported in the study were consistent with other published findings, whereas rates of asthma were higher than previously reported. Notably, the patient population consisted primarily of children from urban and suburban communities in a single region; a review of children’s medical records from rural areas or from different regions might yield different results.
The study also examined incidence and prevalence of a fourth allergic condition, eczema. In the birth cohort, incidence of eczema was 15.3 percent, while the prevalence of eczema in the cross-sectional cohort was 6.7 percent, which is lower than in previous reports. While this retrospective cohort study did not discuss food allergy as a risk factor for eczema, other published studies have reported that about one-third of children with moderate to severe eczema have well-documented food allergies.
Some researchers have used the term “allergic march” or “atopic march” to describe a progression from eczema and food allergies in the first years of life to asthma and rhinitis in later childhood. The CHOP retrospective cohort study indicates a significant link between diagnosed food allergy and subsequent respiratory allergies. As food allergy and asthma diagnoses have increased in recent decades, further research to uncover the mechanisms underlying IgE-mediated disease is needed to protect children’s health and improve their quality of life.