Fennel is in the Apiaceae family of plants which also includes carrot, coriander, dill, parsnip and parsley.

There are no recorded allergens for fennel by the World Health Organization (WHO), because there have not been enough study into allergic effects from this food. If you are interested in what is needed by the WHO before they add an allergen to their allergen database you can check that out HERE.

Fennel has been shown to contain Lipid Transfer Protein (LTP), these are panallergens with the potential to cause allergic reactions over large groups of foods.

Fennel is also though to contain plant profilin proteins, which are also panallergens which are food in lots of different groups of food.

Fennel also contains furanocoumarins. These chemicals can get on the skin and in combination with ultraviolet light (sunlight) can cause a sunburn like rash. Furanocoumarins are found in higher concentrations in fresh herbs and are natural irritants which can cause allergic contact dermatitis. This is more common in occupations where you are frequently coming into contact with the food, like chefs, cooks, growers and pickers.

It is sometimes found in toothpastes and mouthwashes, which is important to note if you think you are allergic to fennel.

Fennel is a high FODMAP food. stands for Fermentable oligosaccharides, disaccharides, monosaccharides and polyols. Foods high in FODMAPs can cause symptoms of food intolerance, affecting the gastro intestinal system and this can be mistaken for a true IgE food allergy.

Fennel is a food moderate in salicylates. Salicylates have the potential to cause worsening of asthma, swelling, itching and hives as well as food intolerance symptoms in people who are sensitive to salicylates.

You can read more about Food Intolerances on the dedicated Food Intolerance Page.

Allergy to fennel is linked to Celery-Mugwort-Spice Syndrome, which is a subtype of Pollen Food Allergy Syndrome. This syndrome affects individuals who have become sensitised to pollen and then have oral allergy type symptoms to foods with similarly shaped proteins. The most common form of Pollen Food Allergy Syndrome is the one caused by birch tree pollen. In Celery Mugwort Spice Syndrome the sensitising pollen is mugwort.

Fennel may also be a food to avoid if you have LTP Syndrome, if you cannot eat fennel even after it has been processed or cooked you may have LTP Syndrome.

The foods most commonly linked to Celery-Mugwort-Spice Syndrome are peach, melon, celery, carrots, camomile, fennel and other spices from the Apiaceae family which include coriander, caraway seed, celery, chervil, cumin, dill, aniseed and parsley.

Profilins are also found as food allergens in kiwi, celery, peanut, chilli, watermelon, orange, hazelnut, melon, carrot, strawberry, soya, walnut, lychee, lupin, apple, cherry, almond, peach, pear, mustard, tomato and aubergine.

Other plants containing profilin inhalant allergens are ragweed, wormwood, birch, sunflower, olive, plantain, poplar and oak.

Common foods involved in LTP allergy include kiwi, strawberries, sunflower seeds, walnut, apple, mulberry, banana, pea, apricot, cherry, plum, almond, peach pomegranate, raspberry, tomato, grape, celery, peanut, asparagus, cabbage, broccoli, chestnut, lemon, tangerine, orange, hazelnut, lettuce, lentils, lupin, green bean, pear, mustard, wheat and maize.

Note that these food lists are not exhaustive, the most up to date information is on the Cross Reactivity Tool.

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