Allergy to celery tuber (celeriac), a member of the Apiaceae family, belongs to the most frequent pollen-related food allergies in some European countries such as Switzerland, France, or Germany. Celery is consumed as raw or cooked vegetable. Severe allergic reactions to celery are mainly observed after ingestion of raw celery but can also occur after intake of foods containing technologically processed or heated celery roots. This is particularly important since dried powder from celery roots is used as a cheap spicing ingredient in many processed foods such as spice mixtures, soups, broths and salad dressings. The allergenicity of celery spice has been shown for patients with known allergy to raw celery in our recent food challenge studies. Thus, commercially used celery powder is not safe for patients who are allergic to raw celery. Furthermore, the allergenic potential of celery was sustained for some patients even after extensive thermal treatment (>60min, at a temperature of 100°C), suggesting a high heat resistance of some of the celery allergens.
Local reactions in the mouth such as itching, but also systemic reactions affecting the skin, the nose and lungs and the stomach or severe life threatening reactions (anaphylaxis) have been observed upon ingestion of celery. Compared to allergic reactions to other fresh vegetables the course of celery allergy is often more severe. During challenge studies with celery, 50% of patients developed local reactions in the mouth and 50% systemic reactions. In a number of patients systemic symptoms were even observed after contact of celery with the mouth without actual ingestion of the allergenic food.
How much is too much?
The minimal dose eliciting allergic symptoms (threshold doses) has not been determined so far. However, 48% of patients undergoing oral provocations with celery developed allergic symptoms at a dose of 700 mg.
Related foods (cross reactivity)
Allergy to celery is frequently associated with birch and or mugwort pollinosis. Therefore, the term birch-mugwort-celery-syndrome has been established. Birch pollen and celery allergy are closely related in Central Europe, while celery allergy develops more frequently in patients with sensitisation to mugwort pollen in Southern Europe. Moreover, allergy to carrot and spices is highly associated to celery allergy. Celery allergic patients may develop a spice allergy, in particular to members of the Apiaceae family such as parsley, coriander, cumin, aniseed, but also to bell pepper and pepper. Allergenicity of stick celery and celery seed, which are used for spicing and for aroma production have not been scientifically evaluated in challenge studies so far.
Who, when, how long, and how often?
In Switzerland about 40% of patients with food allergy are sensitized to celery root, and severe anaphylactic reactions have been reported. In France, 30% of severe allergic reactions to foods were thought to be due to celery according to patients’ history.
For diagnosis skin testing with celery extract may be performed, or blood samples may be measured. Up to 85% of patients with celery allergy depict positive results in these tests. If raw celery is used for skin testing 96 % of celery allergic patients are skin test-positive. Patients with allergy to birch or mugwort pollen, however, may show positive skin test/in vitro results to celery without being affected by allergic symptoms after celery consumption. Thus, positive test results have to be interpreted on the background of a positive case history and/or oral exposure tests.
Due to its high allergenic potency celery is included into the list of foods for mandatory labelling according to the revised EU Labelling Directive 2003/89/EG.