Table of Contents

f276 Fennel seed Scientific Information Summary Allergen Epidemiology Clinical Relevance Molecular Aspects Compiled By

Whole Allergen

f276 Fennel seed

f276 Fennel seed Scientific Information

Type:

Whole Allergen

Display Name:

Fennel seed

Route of Exposure:

Ingestions as food

Family:

Apiaceae

Species:

Foeniculum vulgare

Latin Name:

Foeniculum vulgare

Other Names:

Fennel, Florence fennel, Finocchio, Sweet fennel, Wild fennel, Common fennel, “Sweet Anise”

Summary

Fennel is a herb widely used in cooking, which can be eaten fresh or as a seed. Clinical reports of fennel allergy are rare and limited to case reports, with the majority being in oral allergy syndrome (OAS) patients who are typically pollen-sensitized, especially to birch and mugwort. Cross reactivity has also been observed to peach and celery allergens.

Allergen

Nature

Fennel belongs to the Apiaceae family of aromatic plants, which also includes anise, coriander, cumin, dill, parsley, carrot and parsnip (1). The fennel plant is hardy and perennial, with yellow flowers and feathery leaves. Fennel is consumed as an edible herb in savory dishes, sauces, liqueurs and confectionary (2). As well as its wide use as a spice in cookery, it is also used as an aromatic in various medicinal products and occasionally as a flavor enhancer in toothpaste (1). In Northern Europe the seeds are more commonly eaten, whereas the fresh plant is often consumed in Mediterranean countries. Fennel contains abundant linoleic acid and other fatty acids in the shoots, stems, and inflorescences, giving it a valuable nutritional composition (3).

Taxonomy

Taxonomic tree of Fennel (4)
Domain	Eukaryota
Kingdom	Plantae
Phylum	Tracheophyta
Subphylum	Spermatophytina
Class	Magnoliopsida
Family	Apiaceae
Genus	Foeniculum

Taxonomic tree of Fennel (4)

Epidemiology

Worldwide distribution

Allergy to spices is infrequent, accounting for about 6.4% of all food allergies in adults (5). Accordingly, mono-allergy to fennel is unusual, even among those sensitized to other Apiaceae (1, 6).

A large clinical study was carried out to determine the prevalence of Apiaceae based on carrot, celery, and fennel hypersensitivity in patients with birch pollen allergy. A total of 196 birch pollen-hypersensitive patients with OAS caused by different vegetable foods were examined, of which only one patient had Apiaceae allergy alone (6).

Another study addressed allergic sensitization to coriander, caraway, celery or fennel by skin prick testing in 589 patients, where 32% of children and 23% of adults were positive. However, only 3 patients (0.5%) were thought to have a clinical allergy to fennel (1).

Clinical Relevance

Allergic rhinitis

Clinical reports of fennel allergy are rare, with the majority being birch and mugwort pollen-sensitized patients. This phenomenon is part of the general pollen-food allergies). There are adult case reports of such highlighting the cross-reactive nature of fennel. For example, a 20-year-old man with a history of mild grass pollen allergy experienced anaphylaxis (generalized urticaria, dysphonia, angioedema of the lips, palmar-plantar itch) after ingesting raw fennel, which resolved following the administration of systemic steroids and oral cetirizine. Another 41-year-old man with seasonal rhinitis experienced episodes of OAS and dyspnea after ingestion of raw and cooked fennel. Both were positive to fennel after skin prick testing. Similarly, A 34-year-old woman with a pollen allergy reported OAS with the ingestion of both fennel and cucumber (7).

Cases of allergy to fennel are rarely reported in children. One case study has been described in an 11-year old boy with seasonal allergic rhinitis following contact with toothpaste containing fennel. He presented with sneezing, nasal congestion, sinus pain, vomiting and abdominal pain, difficulty breathing, and palpitations. His serum specific IgE test result to fennel was positive as well as a skin prick test to fennel-flavored toothpaste (1).

Molecular Aspects

Allergenic molecules

Table adapted from Allergome.org (9).

Allergen	Source
Foe v [Leaf]	Apiaceae, Fennel, Foeniculum vulgare, Plants
Foe v [Bulb]	Apiaceae, Fennel, Foeniculum vulgare, Plants
Foe v [Seed]	Apiaceae, Fennel, Foeniculum vulgare, Plants
Foe v 1	Apiaceae, Fennel, Foeniculum vulgare, Plants
Foe v 2	Apiaceae, Fennel, Foeniculum vulgare, Plants
Foe v 3	Apiaceae, Fennel, Foeniculum vulgare, Plants
Foe v 5	Apiaceae, Fennel, Foeniculum vulgare, Plants
Foe v 60kD	Apiaceae, Fennel, Foeniculum vulgare, Plants

Allergen	Source

Several allergens in fennel have been identified, including Foe v 1 (Bet v 1-related protein), Foe v 2 ( profilin) and Foe v 3 (lipid transfer protein) (1, 10).

Cross-reactivity

Cross reactivity has been demonstrated to birch (Bet v 1) and peach (Pru p 3) (1, 10). Homologous protein allergens may also exist with mugwort pollens, accounting for the mugwort-celery-spice syndrome (1, 11). A 60 kDa allergen, highly homologous to a celery allergen (Api g 5), has been recognized in fennel by patients’ IgE. Inhibition experiments showed a high degree of cross-reactivity between this fennel allergen and a homologous mugwort pollen allergen (11). The cross-reactivity seems to be clinically relevant as there is improvement of a patient’s OAS to fennel, cucumber, and melon after pollen-specific injection immunotherapy with a product containing grass, mugwort (50%) and ragweed (50%) allergens (1). Fennel allergens also show homology and cross-reactivity with other Apiaceae family members, such as celery (Api g 5) (11).

Compiled By

Author: RubyDuke Communications

Reviewer: Dr. Michael Thorpe

Last reviewed:January 2022

References

Denaxa D, Arkwright PD. Fennel as a cause of immediate hypersensitivity to toothpaste. Ann Allergy Asthma Immunol. 2020;125(1):99-100.
Das L. Herbal Fortification of Bread with Fennel Seeds. Food Technology and Biotechnology. 2013;51.
Melfi MT, Kanawati B, Schmitt-Kopplin P, Macchia L, Centonze D, Nardiello D. Investigation of fennel protein extracts by shot-gun Fourier transform ion cyclotron resonance mass spectrometry. Food Res Int. 2021;139:109919.
ITIS. Foeniculum vulgare (fennel): Integrated Taxonomic Information System 2021 [cited 2021 11.11]. Available from: https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=29509#null.
Moneret-Vautrin DA, Morisset M, Lemerdy P, Croizier A, Kanny G. Food allergy and IgE sensitization caused by spices: CICBAA data (based on 589 cases of food allergy). Allerg Immunol (Paris). 2002;34(4):135-40.
Asero R. Relevance of pollen-specific IgE levels to the development of Apiaceae hypersensitivity in patients with birch pollen allergy. Allergy. 1997;52(5):560-4.
Asero R. Fennel, cucumber, and melon allergy successfully treated with pollen-specific injection immunotherapy. Annals of Allergy, Asthma & Immunology. 2000;84(4):460-2.
White JML, Pink AE. English Sunday lunch dermatitis: Allergic contact dermatitis to parsnip, carrot, fennel (and ivy). Contact Dermatitis. 2020;83(4):317-8.
Allergome.org. Fennel. Allergomeorg. 2021.
Pastorello EA, Farioli L, Stafylaraki C, Scibilia J, Giuffrida MG, Mascheri A, et al. Fennel allergy is a lipid-transfer protein (LTP)-related food hypersensitivity associated with peach allergy. J Agric Food Chem. 2013;61(3):740-6.
Borghesan F, Mistrello G, Amato S, Giuffrida MG, Villalta D, Asero R. Mugwort-fennel-allergy-syndrome associated with sensitization to an allergen homologous to Api g 5. Eur Ann Allergy Clin Immunol. 2013;45(4):130-7.