|Allergen Data Collection - Update:
Hazelnut (Corylus avellana)
|Authors in alphabetical order [contact
Two fundamentally different types of allergy to hazelnuts have been
identified. The more frequent type is associated with pollens from trees
of the order Fagales (birch, alder, hazel, hornbeam, and oak), the other
less common type is not associated with pollen allergy. Symptoms of hazelnut
allergy in subjects with pollinosis are usually milder immediate-type reactions
at the mucosa of lips, tongue and throat (oral allergy syndrome). In contrast
in hazelnut allergic subjects without concomitant pollinosis more severe
systemic reactions can occur. Even deaths confirmed as due to hazelnut
allergy have been reported.
Prevalence of IgE-mediated adverse reactions to hazelnut in tree pollen allergic patients can be higher than 70%. In Switzerland more than one third of food allergic adults suffer from hazelnut allergy. Hazelnut is often used as a food ingredient in, for example pastry, confectionary products and ice cream. Hazelnut oils which are not fully refined may potentially be a threat for nut allergic individuals.
Useful tests in the diagnosis of hazelnut allergy include skin tests and determination of specific IgE, when positive. In contrast specificity and negative predictive values of these tests are not valid to exclude a hazelnut allergy.
Hazelnut allergens closely related to birch pollen allergens Bet v 1 and Bet v 2 and allergens not related to pollen have been identified in both in subjects with pollinosis and in subjects without pollinosis. Up to now four isoforms of the major allergen Cor a 1 have been identified in hazel pollen (Cor a 1.01 to Cor a 1.03) and hazelnuts (Cor a 1.04), which are cross- reactive to the pathogenesis-related protein Bet v 1. A 14-kDa hazelnut allergen showed cross- reactivity to birch profilin (Bet v 2). These birch-related allergens are labile to heat and enzymatic digestion. One of the allergens not related to pollens belongs to the group of lipid-transfer proteins which were recently identified as plant-pan allergens. These allergenic proteins were demonstrated to be stable against heat treatment.
Detailed information on prevalence, symptoms, and diagnostic features
of hazelnut allergy as well as cross-reactivities, molecular biological
and allergenic properties of the major hazelnut and hazel pollen allergens
are reviewed in tabular form. The terms "nuts" or "tree nuts" refer to
shell (nut) fruits of various botanical families. In the present Allergen
Data Collection nuts or tree nuts include almond, brazil nut, cashew nut,
hazelnut, pecan nut, pistachio, and walnut. Unless stated otherwise, peanuts,
chestnut, and coconuts are not included.
The reference lists of the Allergen Data Collections are based mainly on searches of Medline and FSTA (Food Science & Technology Abstracts) databases up to the related dates of publication. The scientific rigor of the studies listed is variable and not subject of critique or evaluation by the authors or the editor of the Allergen Data Collections. The reader should be aware of considerable problems in comparing data from different studies (eg. patient cohorts, diagnostic performances, possible flaws in allergen preparations and methodologies for allergen characterization) and is encouraged to review the original publications.
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