Lemons are in the Rutaceae family of plants, other fruit in this family include oranges, grapefruit, kumquat, lime and sichuan pepper.

The allergen associated with lemon allergy is called Cit l 1.

Cit l 1 is a Lipid Transfer Protein (LTP), these proteins are resistant to heat and are found in many types of plants. Patients suffering from a more severe allergy to cooked fruit may be sensitised to this group of proteins.

Lemons also contain limonene, which is a component of the oils found in the peel of certain fruits. Limonene is a well known skin irritant - so may cause sufferers to react to the skin whilst being able to eat or drink the fruit.

There is an increasing amount of research into citrus seed allergy - it has been suggested that some allergic reactions have been triggered not by the fruit or peel, but by accidental consumption of the seeds. These allergic reactions may be triggered by proteins found in more commonly eaten seeds (like sunflower and pumpkin seeds) - seed storage proteins.

Like other citrus fruits lemons contain 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.

Citrus fruits are considered to be high in histamine, so should be avoided for those who avoid high histamine foods.

Bottled lemon juice can be high in sulphites. Fresh lemons are lower in sulphites. Sulphites are inorganic salts used in preservations and have the potential to cause symptoms of food intolerance to those sensitive to sulphites, this food intolerance is more common in asthmatics. An improvement in symptoms can be made with a change to a low sulphite diet.

Lemons are low in salicylates. Salicylates in food have the potential to cause gastrointestinal food intolerance symptoms in people who are sensitive to salicylates.

Lemons are a low FODMAP food so are suitable for those following this diet. FODMAP 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.

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

You may be suffering from LTP Syndrome if you have reactions to various fruits, vegetables and nuts and your reactions continue to be severe after you have discarded the peel and have cooked the food.

Eating lemons is also associated with phytophotodermatitis. This is a skin condition that occurs when a person gets the juice from the fruit on the skin and doesn't wash it off. The furocoumarins in the juice of the fruit are activated by the sun and cause an itchy rash on the skin.

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.

Lemon allergens have shown cross-reactivity with the major peach allergen Pru p 3.

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