Hazelnut allergy: proteins, processing and detection methods
What it found
Hazelnut allergy is common and can be severe, and the proteins that cause it are well studied.
Processing can reduce but not remove the allergens, and several lab tests can detect hazelnut in food.
What they found
Studies in people
Prevalence
Hazelnut allergy affects 0.5% to 1% of the general population, with higher rates in children. In Europe, prevalence varies from 0.1% to 2.5% by country.
Symptoms
Reactions range from mild oral allergy syndrome to severe anaphylaxis. People with birch pollen allergy are more likely to react to hazelnuts.
Studies in people and animals
Processing effects
Roasting at 140°C for 40 minutes reduced allergenicity, but 29% of patients still had allergic symptoms. Boiling and baking can also reduce allergenic properties, while high-pressure processing had little effect on immunoreactivity.
Cross-reactivity
Hazelnut allergens can cross-react with other tree nuts, peanuts, and some fruits and vegetables. This is due to similar protein structures.
Other findings
Allergen proteins
Hazelnut allergens include Cor a 1, Cor a 2, Cor a 8, Cor a 9, Cor a 10, Cor a 11, Cor a 12, Cor a 13, Cor a 14, Cor a 15 and Cor a TLP. Some are stable to heat and digestion, while others are easily broken down.
Detection methods
ELISA, lateral flow devices, mass spectrometry and PCR can detect hazelnut allergens in food. ELISA kits can detect hazelnut proteins down to 0.3 mg/kg, and dipstick tests down to 1 mg/kg.
What the authors conclude
“One important factor to reduce but not to eliminate the exposure to hazelnut allergens is food processing.”
Also in their conclusions
- They highlight the need for multidisciplinary efforts to enhance the safety of products containing hazelnuts.
- They state that food processing is important to reduce but not eliminate exposure to hazelnut allergens.
- They suggest that innovations in ingredient labeling and cross-contamination avoidance can further protect consumers with hazelnut allergies.
How it was done
Hazelnut allergy is a significant public health problem in developed countries, and eating hazelnuts can cause severe reactions. The authors wanted to review current knowledge to improve food safety and management for people with hazelnut allergy.
The authors reviewed published research on hazelnut allergens, how common hazelnut allergy is, how food processing affects allergenicity, and methods to detect hazelnut in food.
What it can’t tell you
- This is a review of published studies, so it cannot provide new experimental data on hazelnut allergy.
- The studies reviewed used different methods and populations, so results may not apply to everyone.
- It cannot show whether any specific processing method makes hazelnuts safe for all allergic people.
Who paid
- Funding
- Funded by National Key Research and Development Program of China; National Natural Science Foundation of China; Fundamental Research Funds for the Central Universities (from the PubMed record).
- Conflicts
- The authors have confirmed that there are no conflicts of interest. None of the authors has interests in promoting a biosensor or something else commercial.
- Authors work at
- Southeast University, China; McGill University, Canada
The paper
- Title
- Update on hazelnut allergy: Allergen characterization, epidemiology, food processing technique and detecting strategy
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Camus-Ela M, Wang Y, Rennie GH, Raghavan V, Wang J (2025). Update on hazelnut allergy: Allergen characterization, epidemiology, food processing technique and detecting strategy. Comprehensive reviews in food science and food safety. doi:10.1111/1541-4337.70098Free full textPubMed 39898897DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error