Grapefruits are in the Rutaceae family of plants. Other plants in this family include, oranges, limes and lemons.

Other citrus fruits contain Lipid Transfer Proteins (LTPs). It has been suggested that grapefruit also contain these proteins. LTPs are panallergens with the potential to cause severe allergic reactions.

Grapefruit contains pectin, which has also been shown to cause allergic reactions in some individuals.

Oranges contain gibberellin proteins, there is a possibility that these are also present in grapefruits.

It is strongly advised to avoid eating grapefruit if are taking certain medicines. This is because grapefruit contains naringin, bergamottin and dihydroxybergamottin, all are involved in inhibition of a protein called CYP3A4. The lack of this protein can drastically alter how medications work in the body.

Like other citrus fruits grapefruits 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.

Grapefruit is a low FODMAP food, 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.

Fresh grapefruits are high in salicylates, grapefruit juice is moderate. 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.

Grapefruit allergy is linked to Food Dependent Exercise Induced Anaphylaxis, but the allergenic protein responsible for this has not been identified.

Grapefruit is also linked to Latex Food Syndrome. This is usually caused by hevein, chitinase or profilin proteins. To date none of these proteins have been identified in the skin of grapefruits, so it is not known what causes this.

Other foods containing gibberellins include apricot, peppers, cherries, chilli, oranges, peaches and pomegranates.

Foods containing hevein or chitinase proteins (linking them to Latex Food Syndrome) are avocado, banana, chestnut, coffee, corn, kiwi, pomegranate, apricot, cassava, dill, goji berry, potato, swede and turnip.

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

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