See: Hazelnut tree, for information on Hazelnut tree pollen
Common names: Hazel, Hazelnut, Filbert, Cobnut, Cob. The terms Filbert and Hazelnut are often used interchangeably to include all plants in the genus Corylus, such as C. silvestris, C. maxima and C. colurna.
Common hazelnut is classified as Corylus avellana, Filbert as Corylus maxima.
Other varieties are the Barcelona nut and Cob nut.
These wild nuts grow in clusters on the Hazel tree in temperate zones around the world. Hazel is an aggressive spreader and is particularly common in Europe as a wild growth, where it has played a significant role in the development of the present forest ecology. Archaeology shows that the nuts were a prehistoric food (and the wood a building material), and that tree populations were not adversely affected by land clearance for Neolithic farming.
The tree grows up to 8m and has a smooth, copper-coloured bark, which peals off in thin papery strips, and twigs covered in thick, reddish, glandular hairs. The fertilised flowers develop into clusters of nuts, which turn brown in October. The fruit, a 2 cm nut, is surrounded by a leafy bract (involucre) and ripens in late summer. The fuzzy outer husk opens as the nut ripens, revealing a hard, smooth shell, within which is a sweet, rich, grape-size nut within a bitter brown skin that is sometimes removed. Italy, Spain, France and Turkey lead the way in hazelnut production. The nuts generally fall in the autumn and are harvested from the ground and then shelled and dried.
Many Hazel trees grow wild, aggressively forming coppices and scrub. Particularly when cultivated, the nuts are used chopped, ground, roasted, blanched, sliced, and as flour and paste in all manner of sweets. They are also eaten whole as a snack (often among mixed nuts). During the Western holiday season, bowls of mixed nuts still in their shells are traditionally served, to be cracked with nutcrackers; Hazelnuts are prominent in these mixtures. Hazelnuts also add flavor and texture to savory items such as salads and main dishes.
Filbert nut is a variety of hazelnut that is popular in baking and as a snack. Hazelnut is widely used, and can be a "hidden" allergen.
Nougat, an ingredient in secondary products, e.g., confections, is a hazelnut product. Hazelnut oil obtained from the tree.
Cor a 1, a 17-18 kDa protein, the major hazelnut allergen. (Wensing 2001 ref.4042 2) (Pastorello 2002 ref.5340 2)
Cor a 1.04 in hazelnut, and three other isoforms - 1.01, 1.02, and 1.03 in hazelnut pollen. (Roux 2003 ref.8304 4) (Hansen 2003 ref.7863 2) (Luttkopf 2002 ref.7865 1)
Cor a 2, a profilin. (Hirschwehr 1992 ref.4840 1)
Cor a 8, a lipid transfer protein. (Hansen 2003 ref.7863 2) (Akkerdaas 2001 ref.4051 5) (Pastorello 2002 ref.5340 2)
Cor a 9, 11S globulin-like protein (Beyer 2002 ref.6876 1)
Cor a 11, a 7S vicilin-like globulin
Cor a 1 is homologues to Bet v 1. The Cor a 1.04 isoform is expressed in at least four sub-forms which are 97-99% identical to each other but share only 63 and 71% identity with hazel pollen isoforms (Cor a 1.01, 1.02 and 1.03) (Roux 2003 ref.8304 4)
Roasting of the nuts significantly reduced the allergenic activity evaluated by SPT, HR, specific IgE, and IgE-inhibition. Sensitization against Cor a 1.04 was found in 16/17 patients and against Cor a 2 in 7/17 patients. None of the patients were sensitized to Cor a 8. (Hansen 2003 ref.7863 2)
Cor a 9, a 40 kDa 11S globulin seed storage protein family member. It is a tree pollen-unrelated hazelnut allergen. (Beyer 2002 ref.6876 1)
Cor a 1 shows high homology to the major birch pollen allergen Bet v 1. Binding of Cor a 1 was severely decreased after heating to 80 °C and higher. No activity of this allergen could be detected in roasted hazelnut meal. (Wensing 2001 ref.4042 2)
Immunoblotting with recombinant hazelnut allergens showed sensitization against Cor a 1.04 in 16/17 patients and against Cor a 2 in 7/17 patients. None of the patients were sensitized to Cor a 8. Roasting of the nuts significantly reduced the allergenic activity. (Hansen 2003 ref.7551 1)
Cor a 9 was recognized by serum IgE from 86% (12/14) of the patients with hazelnut allergy with systemic reactions. (Beyer 2002 ref.6876 1)
A 2S heat stable allergen has also been identified (Akkerdaas 2001 ref.4051 5)
Allergy to hazelnut is most frequently observed in patients with birch pollinosis. This can largely be explained by crossreactive IgE against the major birch pollen allergen Bet v 1 and its homologue in hazelnuts Cor a 1. In addition, profilin and carbohydrate structures can be involved. Symptoms of food allergy in these pollinosis patients are usually mild and restricted to the oral cavity. On the other hand, allergy to hazelnuts without concomitant pollinosis is less common, but symptoms tend to be more severe and are often systemic. In this study, a non-pollen-related allergen, 9 kDa allergen, was identified and is the non-specific lipid transfer protein (nsLTP), an allergen in fruits described by Pastorello et al. IgE antibodies against nsLTP from hazelnut were crossreactive with nsLTPs from fruits, like apple and peach. nsLTP resists proteolysis. (Akkerdaas 2001 ref.4051 5)
The hazelnut major allergens identified to date are an 18-kd protein homologous to Bet v 1 and a 14-kd allergen homologous to Bet v 2. No studies have reported hazelnut allergens recognized in patients with positive oral challenges. All the sera from the patients with positive DBPCFC results recognized an 18- and a 47-kd allergen; other major allergens were at molecular weights of 32 and 35 kd. Binding to the 18-kd band was inhibited by birch extract, indicating its homology with the birch major allergen (Bet v 1), and abolished in roasted hazelnut. The 47-kd allergen is a sucrose-binding protein, the 35-kd allergen is a legumin, and the 32-kd allergen is a 2S albumin. Patients with severe anaphylactic reactions to hazelnut showed specific IgE reactivity to a 9-kd allergen, totally inhibited by purified peach lipid-transfer protein (LTP), which was heat stable and, when purified, corresponded to an LTP. The major allergen of hazelnut is an 18-kd protein homologous to Bet v 1, and the 9-kd allergen is presumably an LTP. Other major allergens have molecular weights of 47, 32, and 35 kd. (Pastorello 2002 ref.5340 2)
May be used as a flavouring.
IGE AND IMMUNE:
Hazelnuts are a common cause of food allergy. Allergic reactions to hazelnuts range from oral allergy syndrome caused by cross-reactivity between tree pollen and hazelnut proteins to severe anaphylactic reactions. In 17 patients challenged by DBPCFC with roasted nuts 5 were positive. The symptoms were generally mild and included OAS (oral allergy syndrome) in all patients. Roasting of the nuts significantly reduced the allergenic activity evaluated by SPT, HR, specific IgE, and IgE-inhibition. (Hansen 2003 ref.7863 2)
The probability of a patient with nut allergy having specific IgE to a particular combination of peanut, hazelnut and brazil nut is similar, whatever their age or sex. The apparent increase in multiple nut reactivity with increasing age may therefore be due to exposure of previously unchallenged sensitivity. The frequency of multiple-nut specificity is sufficiently high that patients should always be tested for allergy to a range on nuts if they have a history of reacting to any nut. (Pumphrey 1999 ref.7807 4)
Hazelnuts are a common cause of food allergy. Allergic reactions to hazelnuts range from oral allergy syndrome caused by cross-reactivity between tree pollen and hazelnut proteins to severe anaphylactic reactions. Extrapolation of the dose-response curve showed that 50% of our hazelnut-allergic population will suffer from an allergic reaction after ingestion of 6 mg (95% CI, 2-11 mg) of hazelnut protein. (Beyer 2002 ref.6876 1)
Twenty-nine hazelnut allergic patients had a positive challenge to increasing dose challenges with hazelnut. Itching of the oral cavity and/or lips was the first symptom in all cases. Additional gastrointestinal symptoms were reported in five patients and difficulty in swallowing in one patient. Lip swelling was observed in two patients, followed by generalized urticaria in one of these. Threshold doses for eliciting subjective reactions varied from a dose of 1 mg up to 100 mg hazelnut protein (equivalent to 6.4-640 mg hazelnut meal). (Wensing 2002 ref.7553 2)
In 5/17 patients the DBPCFC with the roasted nuts were positive. The symptoms were generally mild and included OAS (oral allergy syndrome) in all patients. Roasting of the nuts significantly reduced the allergenic activity evaluated by SPT, HR, specific IgE, and IgE-inhibition. (Hansen 2003 ref.7551 1)
Food-dependant exercise-induced anaphylaxis. (Martin Munoz 1994 ref.1201 1)
24% of 276 adult patients reported asthma or rhinitis symptoms on eating or handling various foods, of which hazelnut, apple and shell fish were the most often named (Eriksson).
The reported incidence of reaction to hazel nut appears to be high (Eriksson). More than 10% of individuals in an allergic population had pronounced symptoms following ingestion of this nut. In a study of patients with unspecified allergies, 68% had IgE to hazelnut.
In a study of 62 patients with nut allergy (adults and children), peanuts were the commonest cause of allergy (47), followed by Brazil nut (18), almond (14), and hazelnut (13) (Ewan 1996 ref.1625 9)
The prevalence in the Netherlands of atopy caused by apple, peach, and hazelnut in patients with tree pollinosis was evaluated. Skin prick tests for apple, peach, and hazelnut were positive in 51 (64.6%), 61 (77.2%), and 71 (89.9%) patients, respectively. Granny Smith showed more positive skin reactions and a better agreement with clinical history than Golden Delicious. RAST for apple, peach, and hazelnut was positive in 53 (68.8%), 13 (16.9%), and 31 (40.3%) patients, respectively. (de Groot 1996 ref.1411 2)
Nut oils may pose a threat to patients with allergy, depending on the method of manufacture and processing. (Teuber 1997 ref.1631 3) Hazelnut or other nut oils may be used in chocolate manufacturing. If not completely cleared of hazelnut allergens, may cause an allergy reaction.
It appears that threshold levels for subjective reactions in hazelnut allergic patients vary from less than 1mg up to doses probably higher than 100mg of raw hazelnut protein. (Wensing 2001 ref.4042 4)
Anaphylaxis in a 20-year-old girl to string bean who also developed urticaria from fresh fennel, boiled cabbage, mustard, commercial hazelnut cream and commercial pear juice. (Asero 2001 ref.4132 9)
In evaluating 163 asthmatic children with food allergy for food-induced asthma, using DBPCFC the most frequent offending foods were, sometimes in association, peanut (30.6%), egg (23.1%), cow's milk (9.3%), mustard (6.9%), codfish (6%), shrimp (4.5%), kiwi fruit (3.6%), hazelnut (2.7%), cashew nut (2.1%), almond (1.5%), garlic (1.2%). (Rance 2002 ref.7671 1)
Severe allergic reaction in a young woman after ingestion of hazelnuts without any association to tree pollen allergy. Unlike the IgE binding pattern of the sera from the patients with pollen-related hazelnut allergy, low molecular weight heat-stable proteins below 10 kDa were identified by the sera from the patients without pollinosis. (Schocker 2000 ref.7875 3)
Eighty-six subjects with a history of symptoms after hazelnut ingestion were recruited from 3 allergy centers (Milan, Zurich, and Copenhagen). All subjects underwent skin prick tests (SPTs) with aeroallergens and hazelnut, as well as having their specific hazelnut IgE levels determined. Diagnosis of clinical relevant food allergy was made on the basis of the DBPCFC. Sixty-seven (77.9%) of 86 subjects had a positive DBPCFC result; 8 were placebo responders, and 11 were nonresponders. Of the 11 nonresponders, 4 had positive open-challenge test results. Of the DBPCFC-positive subjects, 87% also had positive skin test responses to birch pollen extract. (Ortolani 2000 ref.7877 1)
Of a total of 196 birch pollen-hypersensitive patients with oral allergy syndrome (OAS), 195 had apple and/or hazelnut allergy, and 103 had Apiaceae sensitivity; only one patient had Apiaceae (carrot, celery, and fennel) allergy alone. (Asero 1997 ref.1714 4)
Oil is non-allergenic if highly purified and containing no protein. See: Hazelnut oil.
In this study, cacao, banana, egg and hazelnuts were found to be responsible for migraine headaches in children and young adults. On an oligoantigenic diet, 6/12 presented a completed remission of headache, and 5/12 had a significant improvement of the migrainous pattern. (Guariso 1993 ref.2092 3)
The effects on iron absorption of nuts were measured in 137 Indian women. When the absorption from bread and nut meals (walnuts, almonds, peanuts, and hazelnuts) was compared with that from bread meals, the overall geometric mean absorption from the nut meals (1.8%) was significantly less than from the bread meals alone (6.6%). In contrast, coconut did not reduce absorption significantly. All the nuts tested contained significant amounts of two known inhibitors of Fe absorption (phytates and polyphenols) but the amounts in coconut were significantly less than in the other nuts. Fifty milligrams ascorbic acid overcame the inhibitory effects of two nuts that were tested (Brazil nuts and peanuts). This is different from that found previously for soy protein, another potent inhibitor of Fe absorption. (Macfarlane 1988 ref.7810 1)
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Allergy Advisor - Zing Solutions
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