Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist
A 5-year-old girl developed hives 2.5 hours after eating a home-made bread with fennel seeds for the first time. The hives lasted for 48 hours and responded to Benadryl given by her mother. The mother is in the allergy clinic requesting to have her daughter tested for fennel allergy. The patient eats regular food and reports no symptoms of food allergy or intolerance.
Past medical history and medications
Father with allergic rhinitis. Mother with amoxicillin allergy.
The mother took a picture of the lesions with a digital camera (shown below).
Urticaria on foot, with visible wheals. Image source: Wikipedia, GNU Free Documentation License.
What diagnostic test would you suggest?
Food allergy is unlikely cause if the symptoms occur more than 2 hours after food ingestion. Food allergy symptoms typically occur within 5-10 minutes of food ingestion, usually when the patient is still eating the food.
The mother insisted on testing for fennel allergy. An ImmunoCAP test was performed and it was negative to fennel.
What is fennel?
Fennel is a hardy, perennial herb, with yellow flowers and feathery leaves. It is generally considered indigenous to the shores of the Mediterranean, but has become widely naturalized elsewhere. It is a highly aromatic and flavorful herb with culinary and medicinal uses similar to dill.
Fennel flowerheads. Image source: Wikipedia, GNU Free Documentation License.
Fennel seeds. Image source: Wikipedia, GNU Free Documentation License.
How common is fennel allergy?
Fennel allergy is rare. In general, food allergy to spices is infrequent constituting 2% of the totality of food allergies.
Mugwort and birch pollen allergy, and hypersensitivity to spices are frequently associated. Apiaceae spices include anise, fennel, coriander and cumin.
How to diagnose fennel allergy?
Positive skin prick test with freshly prepared fennel seed can confirm fennel allergy. Serum IgE antibodies to fennel can also be measured.
Diagnosis can be established by DBPCFC using powdered spices in capsules.
How to treat fennel allergy?
Avoidance of fennel is the primary mode of therapy of fennel allergy. Fennel, cucumber, and melon allergy was successfully treated with pollen-specific injection immunotherapy in a single case report.
Can fennel be used to treat allergies?
The activation of nuclear transcription factor kappaB has been linked with a variety of inflammatory diseases, including allergies and asthma. The pathway that activates this transcription factor can be interrupted by phytochemicals derived from spices such as turmeric (curcumin), red pepper (capsaicin), cloves (eugenol), ginger (gingerol), cumin, anise, and fennel (anethol), basil and rosemary (ursolic acid), garlic (diallyl sulfide, S-allylmercaptocysteine, ajoene), and pomegranate (ellagic acid). For the first time, therefore, research provides "reasoning for seasoning."
Diagnostic algorithm for food allergy: SAD Child:
1. Symptoms: close relation between specific food intake and symptoms, often affect 2 or more organs
2. Allergy testing: skin prick testing or ImmunoCAP.
3. Diagnostic diet: restricted diet leads to symptoms disappearance or significant reduction.
4. Challenge - oral food challenge.
References: Clinical review: ABC of allergies, Food allergy. BMJ 1998;316:1299, figure.
Food allergy and IgE sensitization caused by spices: CICBAA data (based on 589 cases of food allergy). Moneret-Vautrin DA, Morisset M, Lemerdy P, Croizier A, Kanny G. Allerg Immunol (Paris). 2002 Apr;34(4):135-40.
Fennel, cucumber, and melon allergy successfully treated with pollen-specific injection immunotherapy. Asero R. Ann Allergy Asthma Immunol. 2000 Apr;84(4):460-2.
Spice allergy. Ann Allergy Asthma Immunol. Volume 107, Issue 3, Pages 191-199 (September 2011)
Suppression of the nuclear factor-kappaB activation pathway by spice-derived phytochemicals: reasoning for seasoning. Aggarwal BB, Shishodia S. Ann N Y Acad Sci. 2004 Dec;1030:434-41.
Interactive Allergy Map by Greer Labs. Click your state to find region-specific, common airborne allergens there.
Fennel, from Wikipedia, the free encyclopedia.