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Blood Test Tracker

Cor a 14 (hazelnut) IgE

Measures IgE to Cor a 14, a hazelnut storage protein. It is more often found in people who react to eating hazelnut.

AI-verified against cited sources. Awaiting expert reviewAlso called Cor a 14, f439, rCor a 14LOINC 81788-2

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What it is

Cor a 14 is a protein from hazelnut seeds. It belongs to a family called 2S albumins and stays intact when hazelnut is cooked and during digestion. This test measures IgE, the type of antibody linked to allergic reactions, that your body has made against that one protein. It is often added as a follow-up when a standard hazelnut IgE test is positive, to show what kind of hazelnut sensitization you have. Sensitization means your body has made IgE antibodies to a substance. It does not always mean you are allergic.

Why it matters

A hazelnut IgE test can be positive because of a milder, cross-reacting allergy to birch pollen, or because of a true hazelnut allergy. Cor a 14, like another storage protein called Cor a 9, is more often found in people who react to hazelnut itself, sometimes with whole-body (systemic) reactions. A Cor a 14 result gives your clinician more detail than the whole-hazelnut test. It still doesn't confirm an allergy, and it can't predict how severe a reaction would be.

If it’s high

A result above your lab's usual range means your body has made IgE antibodies to this hazelnut protein. This pattern is seen more often in people who react when they eat hazelnut, sometimes with symptoms beyond the mouth. It doesn't confirm an allergy, and the number can't tell how strong a future reaction would be.

Common causes

  • A true hazelnut allergy
  • Sensitization without symptoms, since IgE tests on their own can't confirm an allergy
  • A weak result of 0.10 to 0.34 kU/L, which labs treat as uncertain

What can help

  • Talk with an allergy specialist about how to read this result together with your history and your other hazelnut results, such as Cor a 1, Cor a 8 and Cor a 9
  • Ask whether a supervised food challenge is appropriate
  • Ask for a written plan for what to do if you have a reaction
  • Ask how to spot hidden hazelnut in foods such as chocolate spreads and baked goods

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: 0–0.1 kU/L. Source: Labcorp, Thermo Fisher Scientific (Phadia), Thermo Fisher Scientific, NIAID / Journal of Allergy and Clinical Immunology, World Allergy Organization Journal, Nutrients, Journal of Allergy and Clinical Immunology.

Labcorp class scale (ImmunoCAP; Labcorp prints component results with the same classes)

  • Class 0: negativebelow 0.1 kU/L
  • Class 0/I: equivocal or low0.1 to under 0.32 kU/L
  • Class I: low0.32 to under 0.56 kU/L
  • Class II: moderate0.56 to under 1.41 kU/L
  • Class III: high1.41 to under 3.91 kU/L
  • Class IV: very high3.91 to under 19.01 kU/L
  • Class V: very high19.01 to under 100.01 kU/L
  • Class VI: very high100.01 and above kU/L

What can affect your result

  • Age: hazelnut allergy looks different in children and adults, and adults more often have a birch-pollen cross-reaction pattern (Cor a 1), which usually causes symptoms in and around the mouth
  • Birch pollen allergy: this tends to make Cor a 1 positive rather than Cor a 14
  • Lab method: results from different labs or assay systems may not be comparable
  • Medicines: antihistamines do not change this blood test, unlike skin prick testing
  • Very high total IgE can produce weak, nonspecific positive results.
  • Different assay systems give different numbers for the same blood sample, so compare results from the same lab and method.
  • Some labs reject samples that are hemolyzed (red cells broken), jaundiced (icteric) or lipemic (very fatty).

Antibody levels usually change slowly, over months to years.

When to talk to a clinician

Call your local emergency number if, soon after eating hazelnut or a food that may contain it, you have trouble breathing, throat tightness, swelling of the lips or tongue, repeated vomiting, dizziness or fainting. See a clinician soon if you get hives, itching or stomach upset after eating nuts.

Questions you could ask

  • Does my history of reactions to hazelnut match these results?
  • How do my Cor a 14 result and my other hazelnut results fit together?
  • Should I see an allergy specialist, and is a supervised food challenge appropriate?
  • What should my plan be if I have a reaction?
  • Do I need to test or avoid other nuts?

Questions people ask

My hazelnut test is positive but Cor a 14 is negative. What does that mean?

It can mean your hazelnut IgE comes from a birch-pollen-related pattern (Cor a 1), which more often causes mouth itching than whole-body reactions. A negative Cor a 14 result doesn't rule out hazelnut allergy, though. In one pooled analysis in children, the chance of hazelnut allergy was still about 14% after a negative Cor a 14 result. An allergy specialist will look at all the results with your history.

Does a high Cor a 14 number mean a severe reaction?

Not necessarily. Cor a 14 is linked to a higher chance of true hazelnut allergy, including reactions beyond the mouth, but no blood test can predict how severe a future reaction will be.

If I react to hazelnut, do I need to avoid all tree nuts?

Not always. IgE to several tree nuts is common (in one summary, about 92% of tree-nut-sensitized people were sensitized to other tree nuts), but fewer, about 12% to 37%, reacted to them. An allergy specialist can guide which nuts to test or avoid.

Show the science and sources

Units

  • 1 kU/L = 1 kU/L
  • 1 kU/L = 1 UA/mL

For clinicians and researchers

ImmunoCAP f439 measures IgE to recombinant Cor a 14, a 2S albumin seed-storage protein. Like Cor a 9 (an 11S globulin), Cor a 14 is heat- and digestion-stable and is associated with systemic reactions, in contrast to Cor a 1 (a labile PR-10 protein shared with birch, mostly local mouth symptoms) and Cor a 8 (a lipid transfer protein, local or systemic reactions). In a Dutch study using ImmunoCAP, IgE to either Cor a 9 of 1 kUA/L or higher or Cor a 14 of 5 kUA/L or higher in children (or Cor a 14 of 1 kUA/L or higher in adults) had specificity above 90% for hazelnut allergy with objective symptoms on challenge; these cutoffs came from one population and are not general. A 2021 pooled analysis in children (cutoff 0.35 kUA/L) estimated the chance of hazelnut allergy at about 73% after a positive Cor a 14 result and about 14% after a negative one, starting from about 39% allergic in the pooled studies, and those probabilities depend on how common allergy is in the group tested. Component results use the same quantitative range as whole allergens (0.1 to 100 kUA/L). NIAID 2010 notes that no test predicts the severity of IgE-mediated reactions, and IgE to a single component should always be read with the whole-hazelnut result, the other components and the clinical history.

LOINC 81788-2 (primary). Specimen: serum.

Sources

  1. Allergen Profile, Hazelnut, IgE With Component Reflexes (test 604734), Labcorp
  2. Sample patient report: Allergen Profile, Hazelnut, IgE With Component Reflexes (test 604734), Labcorp (2019)
  3. ImmunoCAP Specific IgE blood test results: Interpretation (respiratory results interpretation guide), Thermo Fisher Scientific (Phadia) (2023)
  4. ImmunoCAP Seed, Legume and Nut Component Allergens (Thermo Fisher product page for component f425; states component results run from 0.1 to 100 kUA/L), Thermo Fisher Scientific
  5. ImmunoCAP Specific IgE: Hazelnut allergy (testing algorithm), Thermo Fisher Scientific (Phadia) (2026)
  6. Guidelines for the Diagnosis and Management of Food Allergy in the United States: Report of the NIAID-Sponsored Expert Panel, NIAID / Journal of Allergy and Clinical Immunology (2010)
  7. IgE allergy diagnostics and other relevant tests in allergy, a World Allergy Organization position paper, World Allergy Organization Journal (2020)
  8. Component-Resolved Diagnosis of Hazelnut Allergy in Children, Nutrients (2021)
  9. Sensitization to Cor a 9 and Cor a 14 is highly specific for a hazelnut allergy with objective symptoms in Dutch children and adults, Journal of Allergy and Clinical Immunology (2013)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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