Children born during the strict COVID-19 lockdown in Ireland continue to show unusually low rates of food allergy five years later, according to a new study published in Pediatric Allergy and Immunology. Researchers following children enrolled in the CORAL (Impact of Coronavirus Pandemic on Allergic and Autoimmune Dysregulation in Infants Born during Lockdown) study found that the low food allergy rates first observed during infancy have persisted, even as other forms of allergic disease have developed along more typical childhood patterns. The researchers say the findings suggest that changes in lifestyle and environmental exposures during the pandemic may have influenced food allergy risk during a critical period of immune development.
The CORAL study began with 365 infants born in Ireland between March and May 2020, during the country’s first and most restrictive lockdown. That extraordinary period dramatically changed babies’ early environments: families spent more time at home, children had less social contact, infection rates and antibiotic use were reduced, and breastfeeding increased. Researchers also provided families with guidance encouraging the early introduction of allergenic foods. Previous CORAL studies found unexpectedly low rates of food allergy by age two, leading investigators to question whether the effect would disappear as the children grew older or represent a more lasting change. For the five-year follow-up, 209 children participated, including 181 who attended an in-person assessment and 175 who underwent skin-prick testing.
The answer appears encouraging: food allergy remained remarkably uncommon. At age five, just one child had peanut allergy, three had tree nut allergy, none had milk or egg allergy, and one had developed fish allergy. Of the two children with peanut allergy at age two, one had outgrown it; among those with tree nut allergy, two cases resolved while two new cases developed. No new cases of IgE-mediated milk or egg allergy were identified. The researchers noted that the cohort’s overall food allergy prevalence was “substantially lower” than rates reported in major population-based studies conducted before the pandemic.
One possible explanation is the unusual combination of circumstances created by lockdown. The researchers previously proposed that longer breastfeeding, reduced antibiotic exposure and clinician-supported early introduction of allergenic foods may have encouraged the development of oral tolerance. Earlier analysis of these children also identified differences in their developing gut microbiomes, including greater abundance of Bifidobacterium at six months and increased butyrate-producing bacteria at 12 months — patterns that were inversely associated with eczema and positive food-allergy skin tests. The researchers now suggest that the persistence of low food allergy through age five indicates that pandemic-related environmental changes may have influenced risk “beyond infancy, rather than simply delaying disease expression.”
That apparent protection did not extend equally to every type of allergy. Atopic dermatitis, or eczema, declined substantially as the children aged, falling from 21.3% at age two to 10.4% at age five; nearly all remaining cases were mild. Meanwhile, sensitization to airborne allergens increased sharply, from 8.9% at age two to 24% at age five. House dust mites were the most common sensitizer, followed by grass pollen, dogs and tree pollen, and 13% of children were sensitized to multiple airborne allergens. These changes largely resemble the expected progression of childhood allergy, in which inhaled-allergen sensitization becomes increasingly common during the preschool years.
Respiratory disease followed a similarly mixed pattern. About 22% of children had parent-reported wheezing at age five, virtually unchanged from age two, while doctor-diagnosed asthma increased to 10.1%. Wheezing was strongly associated with asthma diagnosis but occurred predominantly in children who had experienced a recent infection. Sensitization to house dust mites and animal dander was also associated with wheezing, although no individual allergen was associated with physician-diagnosed asthma. The researchers caution that asthma can still be an evolving diagnosis at this age and that continued follow-up will be necessary to determine whether the children’s increasing aeroallergen sensitization eventually translates into greater asthma risk.
Taken together, the findings suggest that the unprecedented conditions experienced by babies born during lockdown may have altered some early allergic outcomes without fundamentally changing the usual progression of allergic disease. The authors conclude that “early environmental disruptions may influence the initial expression of atopy,” while not necessarily changing the later pathway through which allergic conditions develop. Most intriguing is the persistence of unusually low food allergy rates despite the children’s return to school, childcare and normal social environments. While the observational study cannot establish that lockdown conditions caused the difference — and the researchers acknowledge limitations including the cohort’s relatively small size, loss to follow-up and predominantly socioeconomically advantaged population — the findings strengthen the case for investigating how breastfeeding, antibiotic exposure, early allergen introduction and the infant microbiome interact during the earliest months of life to influence long-term food allergy risk.
