Hazelnut allergy across Europe dissected molecularly: A EuroPrevall outpatient clinic survey

J Allergy Clin Immunol. 2015 Aug;136(2):382-91. doi: 10.1016/j.jaci.2014.12.1949. Epub 2015 Mar 13.


Background: Hazelnut allergy is birch pollen-driven in Northern/Western Europe and lipid transfer protein-driven in Spain and Italy. Little is known about other regions and other allergens.

Objective: Establishing a molecular map of hazelnut allergy across Europe.

Methods: In 12 European cities, subjects reporting reactions to hazelnut (n = 731) were evaluated and sensitization to 24 foods, 12 respiratory allergen sources, and latex was tested by using skin prick test and ImmunoCAP. A subset (124 of 731) underwent a double-blind placebo-controlled food challenge to hazelnut. Sera of 423 of 731 subjects were analyzed for IgE against 7 hazelnut allergens and cross-reactive carbohydrate determinants by ImmunoCAP.

Results: Hazelnut allergy was confirmed in 70% of those undergoing double-blind placebo-controlled food challenges. Birch pollen-driven hazelnut sensitization (Cor a 1) dominated in most cities, except in Reykjavik, Sofia, Athens, and Madrid, where reporting of hazelnut allergy was less frequent anyhow. In Athens, IgE against Cor a 8 dominated and strongly correlated with IgE against walnut, peach, and apple and against Chenopodium, plane tree, and mugwort pollen. Sensitization to seed storage proteins was observed in less than 10%, mainly in children, and correlated with IgE to nuts, seeds, and legumes. IgE to Cor a 12, observed in all cities (10% to 25%), correlated with IgE to nuts, seeds, and pollen.

Conclusions: In adulthood, the importance of hazelnut sensitization to storage proteins, oleosin (Cor a 12), and Cor a 8 is diluted by the increased role of birch pollen cross-reactivity with Cor a 1. Cor a 8 sensitization in the Mediterranean is probably driven by diet in combination with pollen exposure. Hazelnut oleosin sensitization is prevalent across Europe; however, the clinical relevance remains to be established.

Keywords: EuroPrevall; component-resolved diagnosis; hazelnut allergy; outpatient clinic.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Allergens / immunology*
  • Ambulatory Care Facilities / statistics & numerical data
  • Antigens, Plant / immunology*
  • Betula / chemistry
  • Betula / immunology
  • Carrier Proteins / immunology
  • Corylus / chemistry
  • Corylus / immunology*
  • Cross Reactions
  • Double-Blind Method
  • Europe / epidemiology
  • Female
  • Humans
  • Immunoglobulin E / blood
  • Male
  • Middle Aged
  • Molecular Epidemiology
  • Nut Hypersensitivity / epidemiology*
  • Nut Hypersensitivity / etiology
  • Nut Hypersensitivity / immunology
  • Nut Hypersensitivity / physiopathology
  • Pollen / immunology
  • Skin Tests


  • Allergens
  • Antigens, Plant
  • Carrier Proteins
  • Cor a 8 allergen, Corylus avellana
  • lipid transfer protein
  • oleosin, Corylus avellana
  • Immunoglobulin E