Food Allergy Risk Changes as Children Grow

Sensitization to food allergens can change considerably during the first five years of a child’s life. A large Canadian birth-cohort study shows that sensitization to peanut often develops early and persists, while sensitization to several tree nuts tends to appear later. Some children also lose sensitization to allergen components associated with systemic allergic reactions. Researchers from Karl Landsteiner University (klu Krems) played a key role in the international study. By following children over several years rather than testing them at a single point in time, the researchers were able to trace how sensitization develops in early childhood. Their findings could help doctors and families make better-informed decisions about prevention, diagnosis and treatment.

Food allergy is an important health concern in childhood, and knowing whether an allergy is likely to persist or disappear can affect medical decisions. Sensitization, however, is not the same as an allergy: specific IgE antibodies may be detectable without a child developing symptoms after eating the food concerned. Detailed data on how such sensitization changes during early childhood have so far been scarce for North America. The study, with major contributions from the Department of Pediatric and Adolescent Medicine at University Hospital St. Pölten, a teaching and research site of klu Krems, set out to examine these changes over time.

Allergies in Motion

Especially in young children, a positive allergy test is not necessarily the end of the story. We need to know whether a sensitization persists, disappears or develops later. Looking at individual allergen components gives us valuable information for discussing risks and treatment options with families.”

Thomas Eiwegger, Professor and Head, Department of Pediatric and Adolescent Medicine, University Hospital St. Pölten

The researchers analyzed samples from 500 mother-child pairs taking part in the Canadian CHILD Study, working with colleagues from leading Canadian universities and pediatric research centers. Blood samples were available from the mothers during pregnancy and from their children at one and five years of age. Around 300 individual allergen extracts and components were tested. At age one, specific IgE sensitization was found in 25.3% of the children; by age five, this had risen to 40.4%. The allergens involved changed as well. Egg and peanut were among the main food sensitizers at age one, while peanut and tree nuts predominated at age five. Sensitization to environmental allergens such as cats, dogs, house dust mites and grass pollen also became more common.

Peanut and tree nuts showed notably different patterns. Around half of the children with sensitization to major peanut components already showed it at twelve months and remained sensitized at age five. Important components of cashew, hazelnut, walnut and pistachio, by contrast, were often recognized only later. Sensitization was not always permanent: around one in four children lost sensitization to important 2S albumins during the four-year period. These proteins include major allergen components of peanut, tree nuts and sesame and are useful markers for food allergies associated with systemic reactions.

Therapy with Knowledge

These changes are particularly relevant as treatments for food allergies develop. Oral immunotherapy is now included in treatment guidelines and appears to work particularly well when started early. Knowing whether a sensitization is new, persistent or disappearing can therefore be useful when doctors and families discuss treatment. The authors also point to an important limitation: the study did not include oral food challenges to confirm clinical food allergy. Its findings concern sensitization and do not mean that one in four children outgrow an established food allergy.

The work also builds on expertise in pediatric allergology at klu Krems and University Hospital St. Pölten. Before moving to St. Pölten, Eiwegger established a clinical research program for allergy and anaphylaxis at Toronto’s Hospital for Sick Children, where he worked in patient care, research and teaching. This experience now contributes to the pediatric immunology and allergology focus at klu Krems, linking clinical care with research and advanced allergy diagnostics.