Hazelnut allergy T78.0, T 78.1, L27.-

Pollen allergy: Allergologically hazelnut pollen plays an important role (see tree pollen). Pollinosis is often already noticeable in January. The main allergens of hazelnut pollen are the proteins Cor a1 and Cor a 8.

Food allergy: Allergic reactions to the hazelnuts themselves manifest themselves with increasing frequency (about 40% of patients with food allergy). Sensitization to Bet-v 1 homologous proteins such as Ara h 5 and Ara h 8 is usually due to cross-reactions with pollen allergens. Sensitization to Ara h 9 a non-specific lipid transfer protein is considered a secondary food allergen (especially in Mediterranean countries). Primary sensitization is usually via Pru p3 a peach major allergen.

Previously identified and accepted allergens of Corylus avellana:

• Cor a 1 pathogenesis-related protein, PR-10, Bet v 1 family member: Bet v 1-associated cross-reaction; sensitization occurs by Bet v 1. clinically rare reactions
• Cor a 2(Profilin-associated)
• Cor a 6 Isoflavone reductase homologue
• Cor a 8 Non-specific lipid transfer protein: cross allergen, indicator of primary sensitization by other proteins of the lipid transfer protein group
• Cor a 9 11S storage protein (leguminous): marker allergen, indicator of risk sensitization. The question of a cross-reaction with Cor a 11 is not conclusively clarified.
• Cor a 10 Luminal binding protein
• Cor a 11 7S storage protein (vicilin-like); was found in a study especially in infants who developed systemic reactions after consumption.
• Cor a 12 Oleosin
• Cor a 13 Oleosin
• Cor a 14 2S Albumin: Major allergen; indicator of risk sensitization.

Allergic reactions are acquired by patients with pollinosis to early flowering trees ( birch, alder, copper beech, alder) due to a structural similarity between the allergens of these tree pollen and hazelnut. Food sensitizations to hazelnut allergens (especially Cor a 9, Cor a 14) are often simultaneously sensitized to peanut allergens (Ara h 2).

Hazelnut allergy clinic:

• oral allergy syndrome (about 30%)
• acute allergic urticaria (about 30%)
• Bronchospasm (about 15%)
• anaphylactic shock (about 7%)
• Nausea and vomiting (about 7%).
• Hazelnuts are widely used in various preparations as a food. Hazelnut oil is a high-quality edible oil and is also used in oil painting and in the perfume industry. Hazelnut oils (especially cold-pressed oils) can also cause allergic reactions. In the case of purified, highly refined oils, the allergens are usually heat denatured or removed by filtering processes.

1. Etesamifar M, Wüthrich B (1998) IgE-mediated food allergies in 383 patients under consideration of the oral allergy syndrome Allergology 21: 451-457
2. Fuhrman C et al (2007) Short-term effect of pollen exposure on antiallergic drug consumption. Ann Allergy Asthma Immunol 99: 225-231
3. Eller E et al (2016) Cor a 14 is the superior serological marker for hazelnut allergy in children
   ,independent of concomitant peanut allergy.allergy 71:556-562.
4. Gang K et al (2016) Marker allergens and panallergens in tree and pollen allergy. In: Kleine-Tebbe JK et al (Hrsg) Molecular allergy diagnostics. Springer Publishing House GmbH S177-204
5. Hofer Th, Wüthrich B (1985) Food allergies. II. Frequency of organ manifestations and allergy-causing foods. Switzerland Med Weekly 115: 1437-1442
6. WHO/IUS Allergen Nomenclature Sub-Committee