Fennel seed is a spice which may result in allergy symptoms in sensitised individuals.

NB: Fennel seed should not be confused with Dog Fennel. Furthermore, in the United States, fennel may often mistakenly be named anise.

Fennel Seed Allergy Test: Allergen Exposure

Fennel originated in Southern Europe, and has been used by humans since ancient times. It is also common in Britain, Ethiopia, the Middle East, the Far East, the Caribbean, and parts of South America.

It is an evergreen perennial herb growing to around 1m. There are 2 main types of fennel – both have pale green, celery-like stems and bright green, feathery foliage. The broad, bulbous base is treated like a vegetable. Common fennel is the variety from which the oval, greenish-brown fennel seeds are obtained.

The seeds are available whole and ground and are used in both sweet and savoury foods, as well as to flavour a variety of liqueurs.

Fennel seed tea compresses have been used in traditional medicine to help in a range of digestive problems, including hiccups and colic. Fennel tea is also used to soothe inflamed eyelids and watery eyes, as well as being used as gripe water for infants.

In India, fennel seeds are chewed to prevent bad breath and to aid digestion.

Fennel Seed Allergy Test: Allergen Description

Allergens present in fennel seed have been characterised, including a profilin, and a Bet v 1-related protein.

Fennel Seed Allergy Test: Potential 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, parsley, anise, fennel and caraway, but whether this close cross-reactivity occurs between fennel seed in particular and members of the Apiaceae needs further investigation.

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.

Fennel Seed Allergy Test: Clinical Experience

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.

Data from France covering around 600 cases of food allergy has shown sensitisation to coriander, caraway, fennel or celery in 32% of children tested using a skin prick, and 23% in adults. This may be applicable to fennel seed as well.

In a patient with occupational rhinoconjunctivitis to aniseed, skin-specific IgE tests showed a positive immediate response to aniseed, asparagus, caraway, coriander, cumin, dill, and fennel extracts.

Typical features of oral allergy syndrome may occur after the ingestion of fennel seed.

Other reactions

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.