Fennel

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Code: f276
Latin name: Foeniculum vulgare
Source material: Swollen leave-base from fresh fennel
Family: Apiaceae
Common names: Fennel, Florence fennel, Finocchio, Sweet fennel, Wild fennel, Common fennel, “Sweet Anise”
Synonyms: F. officinale, F. capillaceum, F. foeniculum
 
This plant is not to be confused with Dog Fennel (Anthemis cotula). In the USA, Foeniculum vulgare is often mistakenly called Anise.

Allergen Exposure

Geographical distribution
Fennel is native to southern Europe (where it has been popular since Mycenaean times), and is common there and in Britain, Ethiopia, the Middle East, the Far East, the Caribbean, and parts of South America.

Fennel is an evergreen perennial herb growing to 1.5 m by 1 m. There are 2 main types of this aromatic plant, both with pale green, Celery-like stems and bright green, feathery foliage. Florence fennel, also called Finocchio, is cultivated throughout the Mediterranean and in the United States. It has a broad, bulbous base that is treated like a vegetable. Common fennel is the variety from which the oval, greenish-brown Fennel seeds come.

Environment
Fennel grows in meadows and cultivated beds. Both the base and stems of Florence fennel can be eaten raw in salads or cooked by a variety of methods such as braising, sautéing or boiling in soups. The fragrant, graceful greenery can be used as a garnish or snipped into small pieces like dill. This type of Fennel is often mislabelled “Sweet anise”, but the flavour of Fennel is sweeter and more delicate than Anise. The leaves or the seeds can be used to make a pleasant-tasting herbal tea.

The plant is used as a herbal remedy, including as a gargle and an eyewash.

Unexpected exposure
Yellow and brown dyes are obtained from the flowers and leaves combined. The oil may be used as a flavourant or fragrance in toothpastes, soaps, perfumery, air fresheners, etc.

Allergens
No allergens from this plant have yet been characterised.

A profilin-related allergen to Bet v 1, and cross-reacting allergenic molecules in the molecular weight range of 60 kDa, have been detected in Fennel (1).

A lipid transfer protein has been detected (2).

Potential cross-reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected and in fact is frequently manifested (3). Cross-reactivity among the Apiaceae is the cause of the pattern of positive results obtained with Carrot, Parsely, Anise, Fennel and Caraway (4-6).

As Fennel contains a profilin-related allergen, cross-reactivity between Fennel and other profilin-containing plants is possible (1,7).

Caraway, Fennel, cumin, and Coriander extracts showed similar IgE-binding patterns. Enzyme immunoassay inhibition studies with a serum from a patient allergic to Aniseed revealed cross-reactivity among the IgE components from Aniseed, Caraway, Coriander, Fennel, and Dill extracts (8).

Clinical observations have also been the source of reports that in Mugwort and Birch pollen allergy, hypersensitivity to spices is frequently seen in association (1).

A study suggested that most Apiaceae determinants cross-react with Apple or Hazelnut determinants, whereas only some Apple or Hazelnut determinants cross-react with Apiaceae-allergenic determinants (9).

Clinical Experience

IgE-mediated reactions
Fennel may commonly induce symptoms of food allergy in sensitised individuals. Allergic symptoms may occur in children (10-12). Fennel allergy in children may result in symptoms of food allergy and/or atopic dermatitis (10).

Typical features of oral allergy syndrome (OAS) may occur with the ingestion of Fennel (13-14). Among 196 Birch pollen-hypersensitive patients with OAS caused by various vegetables who were examined in a cross-sectional part of a study, 195 had Apple and/or Hazelnut allergy, and 103 had Apiaceae sensitivity; only a single patient had Apiaceae allergy alone. Apiaceae-positive patients showed significantly higher Birch pollen IgE antibody levels than did negative ones (8).

Food-dependent exercise-induced anaphylaxis following ingestion of Fennel has been reported (15).
The presence of IgE antibodies to Fennel may be detected in serum of sensitised individuals (16). Tests for skin reactivity to native spices have been carried out in patients suspected of food allergies to spices. Frequent sensitisation to Apiaceae (Coriander, Caraway, Fennel, and Celery) was observed in 32% of children and 23% of adults, demonstrating the presence of IgE antibodies to these spices (4,17).

Other reactions
A survey of the literature shows essential oils of 11 plants (Eucalyptus, Fennel, hyssop, pennyroyal, Rosemary, Sage, savin, tansy, Tthuja, turpentine, and wormwood) to be powerful convulsants due to their highly reactive monoterpene ketones (18).

Vegetables containing psoralens are responsible for contact phytophotodermatitis, but they probably do not produce photo-dermatitis when taken orally. In a study, healthy volunteers ingested Celery in large amounts (500 grams and more): plasma concentrations of psoralens were found to be non-existent in all subjects and at all sampling times, and no phototoxic reaction was detected by MPD. The authors report that Celery roots do not appear to be photosensitising, even after ingestion in large amounts, but that they might increase the risk of phototoxicity in PUVA-therapy. The same applies to Fennel and parsnip (19).

Compiled by Dr Harris Steinman, harris@zingsolutions.com

References

  1. Jensen-Jarolim E, Leitner A, Hirschwehr R, Kraft D, Wuthrich B, Scheiner O, Graf J, Ebner C.
    Characterization of allergens in Apiaceae spices: anise, fennel, coriander and cumin.
    Clin Exp Allergy 1997;27(11):1299-306
  2. Asero R, Mistrello G, Roncarolo D, Amato S. Detection of some safe plant-derived foods for LTP-allergic patients. Int Arch Allergy Immunol 2007 May 14;144(1):57-63
  3. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09
  4. Wuthrich B, Dietschi R. The celery-carrot-mugwort-condiment syndrome: skin test and RAST results. [German] Schweiz Med Wochenschr 1985;115(11):258-64
  5. Stager J, Wuthrich B, Johansson SG. Spice allergy in celery-sensitive patients.
    Allergy 1991;46(6):475-8
  6. Helbling A, Lopez M, Schwartz HJ, Lehrer SB. Reactivity of carrot-specific IgE antibodies with celery, apiaceous spices, and birch pollen.
    Ann Allergy 1993;70(6):495-9
  7. Paschke A, Kinder H, Zunker K, Wigotzki M, Steinhart H, Wessbecher R, Vieluf I. Characterization of cross-reacting allergens in mango fruit. Allergy 2001;56(3):237-42
  8. Garcia-Gonzalez JJ, Bartolome-Zavala B, Fernandez-Melendez S, et al. Occupational rhinoconjunctivitis and food allergy because of aniseed sensitization. Ann Allergy Asthma Immunol 2002;88(5):518-22
  9. 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
  10. Rance F, Dutau G. Labial food challenge in children with food allergy.
    Pediatr Allergy Immunol 1997;8(1):41-4
  11. Ottolenghi A, De Chiara A, Arrigoni S, Terracciano L, De Amici M. Diagnosis of food allergy caused by fruit and vegetables in children with atopic dermatitis. [Italian] Pediatr Med Chir 1995;17(6):525-30
  12. Gluck U. Neglected allergens[German] Ther Umsch 1992;49(10):669-73
  13. Asero R. Fennel, cucumber, and melon allergy successfully treated with pollen-specific injection immunotherapy. Ann Allergy Asthma Immunol 2000;84(4):460-2
  14. Gluck U. Pollinosis and oral allergy syndrome. [German] HNO 1990 May;38(5):188-90
  15. Romano A, Di Fonso M, Giuffreda F, Quaratino D, Papa G, Palmieri V, Zeppilli P, Venuti A. Diagnostic work-up for food-dependent, exercise-induced anaphylaxis.
    Allergy 1995;50(10):817-24
  16. Wuthrich B, Hofer T. Food allergy: the celery-mugwort-spice syndrome. Association with mango allergy? [German] Dtsch Med Wochenschr 1984;109(25):981-6
  17. 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
  18. Burkhard PR, Burkhardt K, Haenggeli CA, Landis T. Plant-induced seizures: reappearance of an old problem.
    J Neurol 1999;246(8):667-70
  19. Gral N, Beani JC, Bonnot D, Mariotte AM, Reymond JL, Amblard P. Plasma levels of psoralens after celery ingestion. [French] Ann Dermatol Venereol 1993;120(9):599-603

 

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.