Hazelnut allergy test patterns vary by age and region
What it found
In blood samples from 10,503 people in the United States who tested positive for hazelnut, the proteins they reacted to depended strongly on age and where they lived.
Children under 3 mostly reacted to Cor a 9 and Cor a 14, while adults mostly reacted to Cor a 1.
What they found
Studies in people
Age and protein patterns
Children under 3 were mostly sensitised to Cor a 9 (89.6%) and Cor a 14 (23.1%). Cor a 1 sensitisation rose from 4.7% in children aged 0 to 3 up to 82.5% in adults aged 30 to 40.
Regional differences
Cor a 1 sensitisation was significantly higher in the Northeastern United States than in other regions. Cor a 8 sensitisation stayed near 10% across all ages and regions.
Hazelnut and other nuts
More than 50% of hazelnut sensitised adolescents were also sensitised to peanut. The strongest link between hazelnut and other nut antibodies was in children under 3.
Cross-reactivity patterns
Correlations suggested that reactions to both hazelnut and walnut may come from shared PR-10 proteins, lipid transfer proteins, or seed storage proteins. Hazelnut and peanut reactions were more often linked to shared PR-10 proteins (Cor a 1 and Ara h 8) and lipid transfer proteins (Cor a 8 and Ara h 9).
Component testing coverage
Only 6.7% of hazelnut-positive people had no reaction to any of the four hazelnut proteins tested. The sum of the four component results matched the whole hazelnut result well.
What the authors conclude
“We conclude that sensitization to individual hazelnut components is highly dependent on age and/or geographic location.”
Also in their conclusions
- They conclude that sensitisation to hazelnut storage proteins Cor a 9 and Cor a 14 is more common in children than adults evaluated for suspected hazelnut allergy, while the opposite is true for Cor a 1.
- They say that sensitisation to Cor a 8 occurs at a modest prevalence and appears unrelated to age or geographic region.
- They call for additional studies that include information on patient symptoms to better define the clinical usefulness of hazelnut component testing.
How it was done
Doctors wanted to see whether age and location affect which hazelnut proteins a person reacts to, and how hazelnut reactions relate to reactions to other tree nuts and peanuts.
They analysed stored blood samples from 10,503 people across the United States who had tested positive for hazelnut at 0.35 kU A/L or higher. They measured antibodies to four hazelnut proteins (Cor a 1, 8, 9 and 14), and in some samples also to peanut, walnut and cashew proteins.
What it can’t tell you
- The samples came from people whose doctors had already ordered a hazelnut allergy test, so the patterns may not match the general population.
- The study had no information on whether people actually had allergic reactions to hazelnut, only on their antibody test results.
- The study cannot show that reacting to a particular hazelnut protein causes a particular symptom.
Who paid
- Authors work at
- Center for Esoteric Testing, North Carolina; Uppsala University, Sweden; Johns Hopkins University School of Medicine, Maryland
The paper
- Title
- Sensitization profiles to hazelnut allergens across the United States
- Type
- Study
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Valcour A, Lidholm J, Borres MP, Hamilton RG (2019). Sensitization profiles to hazelnut allergens across the United States. Annals of allergy, asthma & immunology. doi:10.1016/j.anai.2018.09.466Free full textPubMed 30292797DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error