Hazelnut allergy: how long it lasts and how it is treated
What it found
Hazelnut allergy is the most common nut allergy in Europe, usually starts in childhood and often lasts for life.
In people, oral and under-the-tongue immunotherapy raised the amount of hazelnut some patients could tolerate.
What they found
Studies in people
How common it is
Hazelnut is the most frequent nut trigger of whole-body allergic reactions in Europe. Challenge-confirmed tree nut allergy in children is estimated at under 2%, while probable tree nut allergy is estimated at 0.05 to 4.9%.
Reactions and severity
Reactions can range from mild hives and itching to anaphylaxis. Half of all children with nut allergies have an anaphylactic reaction as their first sign, with no significant difference between nut types.
How long it lasts
Tree nut allergies, including hazelnut, tend to persist. One estimate is that only about 10% of young patients may outgrow tree nut allergies.
Pollen cross-reactivity
In birch-endemic areas, many adults with hazelnut sensitization react to Cor a 1, a protein also found in birch pollen. This cross-reactivity usually causes only mild itching and swelling of the tongue and lips.
Storage proteins and risk
Sensitization to the hazelnut storage proteins Cor a 9 and Cor a 14 is linked to a higher risk of severe reactions. Cor a 14 appears to predict moderate-to-severe reactions better than Cor a 9.
Immunotherapy results
In one study of 100 children given oral immunotherapy with ground hazelnuts, 34% could tolerate 1635 mg of hazelnut protein after six months, and the rest could tolerate more than before. In a smaller study of 70 patients, 51.4% reached a tolerated dose above 120 mg after one year, but 2.9% had severe reactions during treatment.
What the authors conclude
“The main goal of AIT is not to cure food allergy but to increase the tolerance of the patient to the culprit food, thus reducing the impact of a food allergy on quality of life, by reducing the risk of severe reactions upon accidental ingestion, as well as food-related anxiety.”
Also in their conclusions
- They conclude that telling apart primary hazelnut allergy from pollen cross-reactions is crucial for accurate diagnosis and treatment.
- They advise that molecular diagnosis, alongside clinical history and skin tests, can help identify patients at risk and reduce unnecessary food challenges.
- They say the main goal of allergen immunotherapy is not to cure food allergy but to raise tolerance and reduce the impact on quality of life, and they call for better-quality studies to set a standard protocol.
How it was done
The authors wanted to pull together what is known about how hazelnut allergy develops over time and about newer ways to diagnose and manage it.
They searched PubMed and the Cochrane Library for articles on hazelnut and allergy published between January 2012 and December 2022, screened titles and abstracts, and added further relevant references found during full-text review.
What it can’t tell you
- This is a review of published studies, so it cannot prove that any treatment or test causes a particular outcome.
- The review reports no data on whether avoiding hazelnut early in life prevents the allergy, and the authors note that trials on this are still ongoing.
- The authors say evidence on hazelnut immunotherapy is still limited, with no standard of care and no data on long-term tolerance.
Who paid
- Conflicts
- The authors declare no conflict of interest.
- Authors work at
- IRCCS Azienda Ospedaliero-Universitaria di Bologna, Italy; University of Bologna, Italy; Azienda Ospedaliero-Universitaria, Italy
The paper
- Title
- Natural History of Hazelnut Allergy and Current Approach to Its Diagnosis and Treatment
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Giannetti A, Ruggi A, Ricci G, Giannì G, Caffarelli C (2023). Natural History of Hazelnut Allergy and Current Approach to Its Diagnosis and Treatment. Children (Basel, Switzerland). doi:10.3390/children10030585Free full textPubMed 36980143DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error