Hazelnut is a food which may result in allergy symptoms in sensitised individuals.

Hazelnut Allergy Test: Allergen Exposure

The hazelnut is a small, hard nut native to Europe and is commercially produced in a number of countries, the leading producers being Italy, Spain, France and Turkey. It is harvested in autumn, when the nuts fall naturally to the ground and are then collected, shelled and dried before further processing. Hazelnuts are also sold in their shells as a common snack food.

The processed nuts are used chopped, ground, roasted, blanched, sliced, and as flour and paste in all manner of sweets. Hazelnuts also add flavor and texture to savory items such as salads and main dishes.

Hazelnut is widely used and can be a “hidden” allergen; for example, nougat, an ingredient in secondary products such as confectionary and desserts, is a hazelnut product.

Hazelnut Allergy Test: Allergen Description

Various allergens have been isolated and characterized in hazelnut, including a Bet v 1 homologue (and major allergen), a profilin, a lipid transfer protein, a thaumatin-like protein, an oleosin and a heat shock protein. Some of these allergens are also present in hazel tree pollen.

Hazelnut Allergy Test: Potential Cross-Reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected. Cross-reactivity between hazelnut and hazel tree pollen may occur.

Where trees of the family Betulaceae (e.g., birch, alder, hazel and hornbeam) are prevalent, the cross-reactivity between sensitising pollen and nut allergens can be the leading cause of food allergies.

Allergy to hazelnuts can be regarded as a common example of birch pollen-related food allergy.

In individuals with kiwi allergy, strong reactions to apple and hazelnut were reported and moderate reactions to carrot, potato and avocado.

An important cross-reactivity among the pollen of Platanus acerifolia (London plane tree), hazelnut and banana has been reported.

Mugwort pollen has also been shown to be cross-reactive with hazelnut allergens.

Partial cross-reactivity has been reported to occur between hazelnut and macadamia nut.

In a study of a patient with anaphylaxis to coconut and oral symptoms to tree nuts, the presence of cross-reactive allergens between hazelnut and coconut was shown.

Allergy to kiwi, poppy seeds and/or sesame seeds often occurs in patients with a simultaneous sensitisation to nuts and flour.

Hazelnut Allergy Test: Clinical Experience

Hazel nuts are a common cause of food allergy. Allergies to peanut and tree nuts (walnut, hazelnut, brazil nut, pecan) frequently have an onset in the first few years of life, generally persist, and may account for severe and potentially fatal allergic reactions.

Allergic reactions to hazelnuts range from oral allergy syndrome to severe anaphylactic reactions.

Allergy to hazelnut is most frequently observed in patients with allergy to birch pollen.

The risk of a patient being sensitised to multiple nuts is sufficiently high that patients should always be tested for allergy to a range of nuts if they have a history of reacting to any nut.

Hidden hazelnut is a threat to allergic patients. This may take the form of hazelnut allergens in hazelnut oil. Hazelnut or other nut oils may be used in chocolate manufacturing.

Occupational allergy to hazelnuts is also a possibility.

Other reactions

Nickel is abundant in hazelnuts.