Diagnostic Workup for Fennel Allergy

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


Family history

Father with allergic rhinitis. Mother with amoxicillin allergy.

Physical examination


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.

Published: 03/09/2009
Updated: 08/09/2011


South Slope said...

Until I read this, I had never come across another person with a Fennell Allergy - I actually react (GI) to raw fennel and I've only ever experienced severe reactions in the Spring (also have EAs to everything!). Fascinating...

Ben said...

Im allergic too! mess's me right up, serious nausea for several days!

Anonymous said...

I'm allergic to fennel, also. After unknowingly eating something with fennel seeds, I will be hit with severe nausea within 6 hours, and then abdominal cramps can last for 1 to 3 days.

Anonymous said...

I just drank fennel tea 2 days in a row. And 10 mins later, my skin appears sunburnt (cheeks,nose), very hot and tight. So uncomfortable. Never knew this was possible.
Question: If one is allergic to fennel, what other things would they be allergic too? (is this part of the Birch family?)

Anonymous said...

I am deathly allergic to it. I have anaphlayatic reaction. Have had at least three near death experiences.. Each time it's much worse. Had a tomato and cucumber salad and the cucumber had been cross-bread with fennel. Each time I have had fennel unknowingly.. Very dangerous. Don't know anyone with this rare allergy.

Anonymous said...

Died and was revived from deadly fennel seed allergy! Watch out for the words "Italian" it might contains fennel.Im also allergic to tomatoes and peanuts as well. Hives. Anaphlyatic shock. Severe swelling.

Anonymous said...

I too am severely allergic, have had two anaphylactic episodes to fennel seeds, which I had unknowingly. Frustration is often ingredients list "spices" and do not detail which ones are used. I must walk around with an epipen in case. Very scary. I keep away from Italian spices,cookies and sausages just in case.

Anonymous said...

I fainted in the kitchen the other day as a result of a severe fennel allergy. Made a veg stew & thought it'd be nice to have toasted rye bread on top. Nope! Steam from stew made fennel swell in the bread & it was 10x stronger in aroma, flavor and (I guess) strength. I'd eaten the whole bowl and the bread. Experienced with recreational drugs, this was unlike anything I've ever felt before and not in a good way! I thought I was dead. It scared the shit out of both my husband & I. I saw glittery yellow-white light, felt warm & went to the floor unconscious. He revived me within 1 minute with his terrified tone of voice (and threat to call an ambulance). He helped me walk down the hall to bed, I detoured to the bathroom & vomited while feeling like I was expelling a demon from my system. I've never even herd of this allergy before!! It was terrifying.

Anonymous said...

I ate sausage pizza one from papa Murphy and the other papa John both times woke up with severe stomach cramps and passed out in the bathroom woke up with a chipped tooth, busted lip and a black eye. Decided fennel was the only culprit in both pizzas.

Jerri Hopper said...

They actually have fennel power which I have been told is 1000x's stronger in that form. I had a "sliver of a taste of a pork rib (smaller than my pinkie nail) and the ribs were marinated in fennel power- un-beknowst to the server and to me.. I almost died... severe anaphylactic reaction, organs were shunting blood-going into shock..... I have to carry 6 EPI -pens with me at all times..Went to a specialist to see if one could be desensitized to it? Got the idea from someone telling me about their child getting shots for peanut allergy to desensitize child- but there is no such thing that works.....Its a complete sensation of impending doom unlike any other.. Would not wish this on anyone... Stay safe people- and carry your EPI pens... By the way, there are now more winning lawsuits in effect for situations where one goes to a restaurant and makes it known that you have an allergy and they serve you food with the allergen in it-causing immediate harm...not only do yo have a right to sue the restaurant, but the individuals as well.