Food Allergies Change As Toddlers Grow Older

A child’s risk of food allergies changes considerably during the first five years of life, both in sensitivity and in the foods they react to, a new study says.

Sensitization to food allergens appears to affect more children over time, researchers reported recently in the journal Allergy.

Further, the foods to which a child might react change as they grow older, the research team found. Peanuts are an early allergen, while allergies to other types of nuts and substances appear later.

“Especially in young children, a positive allergy test is not necessarily the end of the story,” said senior researcher Dr. Thomas Eiwegger, head of pediatric and adolescent medicine at University Hospital St. Pölten in Austria.

“We need to know whether a sensitization persists, disappears or develops later,” Eiwegger said in a news release. “Looking at individual allergen components gives us valuable information for discussing risks and treatment options with families.”

For the study, the team analyzed blood samples from 500 mother-child pairs taking part in a long-term Canadian study.

Children’s blood samples were taken at one and five years old. Researchers tested each sample for 300 different allergen extracts or components to see whether the child had developed any sensitivity.

By age one, a quarter of children (25%) had sensitivity to at least one food, results show. By age five, this had increased to 2 in 5 children (40%).

Egg and peanut were among the main food allergens at age one, but by age five children showed greater sensitivity to tree nuts like cashew, hazelnut, walnut and pistachio, researchers found.

Kids also became more sensitized to environmental allergens like cats, dogs, dust mites and grass pollen as they grew older, researchers said.

Notably, sensitization was not always permanent. About 1 in 4 kids lost sensitization to peanut, tree nut and sesame allergen components as they aged, researchers said.

These results could help guide food allergy treatment, researchers said. For example, doctors might change their approach based on whether a child’s sensitization is new, persistent or disappearing.

“Together, this may help inform shared decision-making for designing allergy treatments in the pediatric population,” the research team wrote. “It also provides important data for designing future clinical trials.” 

More information

Johns Hopkins Medicine has more on food allergies in children and babies.

SOURCES: Karl Landsteiner University, news release, Oct. 14, 2026; Allergy, Sept. 16, 2026