Fennel seed
Summary
This plant is not to be confused with Dog Fennel (Anthemis cotula). In the USA, Foeniculum vulgare is often mistakenly called Anise.
Spice
A spice, which may result in allergy symptoms in sensitised individuals.
Allergen
Allergen Description
Allergens unique to Fennel seed, with molecular weights of 67 to 75 kDa, have been detected.
The following allergens have been characterised:
Bet v 1, a profilin-related allergen, and cross-reacting allergenic molecules with molecular weights around 60 kDa, have been detected in fresh Fennel.
Route Of Exposure
Allergen Exposure
Fennel is native to southern Europe (where it has been popular since Mycenean 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.
Fennel grows in meadows and cultivated beds. The seeds of Common fennel are available whole and ground and are used in both sweet and savoury foods, as well as to flavour many liqueurs. An essential oil from the fully ripened and dried seed is used as a food flavouring in similar ways to the whole seed. Though Common fennel is bulbless, its stems and greenery are also used in the same ways as those of Florence fennel.
Fennel seed tea compresses have been used in traditional medicine to help in a range of digestive problems, from hiccups to colic. Fennel tea is also used to soothe inflamed eyelids and watery eyes. Cooled and weak, the tea can be used as gripe water for infants. In India, seeds are chewed to prevent bad breath and to aid digestion.
Yellow and brown dyes are obtained from the flowers and leaves combined. The oil may be used as a flavourant in toothpastes, soaps, perfumery, air fresheners, etc.
Clinical Relevance
IgE-mediated reactions
Fennel seed may induce symptoms of food allergy, rhinoconjunctivitis and asthma in sensitised individuals.
Occupational allergic rhinoconjunctivitis and asthma to Fennel seed have been reported.
Typical features of oral allergy syndrome (OAS) may occur after the ingestion of Fennel. Among 196 Birch pollen-hypersensitive patients with OAS caused by different 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 1 patient had Apiaceae allergy alone. Apiaceae-positive patients showed significantly higher Birch pollen-specific IgE levels than did negative ones. This may be applicable to Fennel seed as well.
Skin-specific IgE tests 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, with 32% of children and 23% of adults demonstrating the presence of specific IgE to these spices. This may be applicable to Fennel seed as well.
Other reactions
A survey of the literature shows essential oils of 11 plants to be powerful convulsants (Eucalyptus, Fennel, hyssop, pennyroyal, rosemary, Sage, savin, tansy, thuja, turpentine, and wormwood) due to their highly reactive monoterpene ketones.
The oils of Fennel seed contain anethole, fenchone, camphene, sabenine, myrcene, limonene, camphor, and several other volatile constituents. Skin contact with the sap or essential oil is said to cause photosensitivity and/or dermatitis in some people. Ingestion of the oil can cause vomiting, seizures and pulmonary oedema.
See also Fennel, fresh (another description of Foeniculum vulgare).
Cross-Reactivity
An extensive cross-reactivity among the different individual species of the genus could be expected and in fact is seen frequently. Cross-reactivity among the Apiaceae is the cause of the pattern of positive results obtained with Carrot, Parsely, Anise, Fennel and Caraway, but whether this close cross-reactivity occurs between Fennel seed in particular and members of the Apiaceae needs further investigation.
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.
As Fennel contains a profilin-related allergen, cross-reactivity between Fennel and other profiling-containing plants is possible, but whether this type of allergen is present in Fennel seed has not been determined yet.
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.
References
- Schwartz HJ, Jones RT, Rojas AR, Squillace DL, Yunginger JW. Occupational allergic rhinoconjunctivitis and asthma due to fennel seed. Ann Allergy Asthma Immunol 1997;78(1):37-40.
- 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.
- Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09.
- Wuthrich B, Dietschi R. The celery-carrot-mugwort-condiment syndrome: skin test and RAST results. [German] Schweiz Med Wochenschr 1985;115(11):258-64.
- 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.
- 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.
- 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. Ann Allergy Asthma Immunol 2000;84(4):460-2.
- 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.
- Stager J, Wuthrich B, Johansson SG. Spice allergy in celery-sensitive patients. Allergy 1991;46(6):475-8.
- Burkhard PR, Burkhardt K, Haenggeli CA, Landis T. Plant-induced seizures: reappearance of an old problem. J Neurol 1999;246(8):667-70.