Grapefruit, orange, and lemon are the principal members of the citrus family. Grapefruit is a subtropical citrus tree grown for its fruit. Its origin is not clear, but it may originally have been a hybrid of the pomelo and the sweet orange tree. Tangelo is a hybrid of grapefruit and orange, and has a less bitter taste than grapefruit.

Grapefruit is pinkish- to yellow-skinned and oblate to round, ranging in diameter from 10 to 15 cm. The most popular varieties cultivated are referred to by the colour of the segmented pulp, which can be red, white, or pink. Grapefruit flavour ranges from highly acidic and somewhat bitter to sweet and tart. Unlike other citrus fruits, grapefruit contains mercaptan, a terpene partly composed of sulphur; mercaptan has a strong influence on the taste and odour of the fruit.

IgE-mediated reactions

Citrus fruits such as grapefruit are among the most common causes of atopic dermatitis. (1-4) IgE antibodies to grapefruit were detected in patients with atopic dermatitis, allergic rhinitis, and bronchial asthma. (5) In a study of children with atopic dermatitis, many were shown to have serum-specific IgE directed against grapefruit. (6) Many patients were also found positive in a similar study of adults. (7) An instance of food-dependent exercise-induced anaphylaxis (FDEIA) attributed to grapefruit has been reported. (8)

A study was conducted at 17 clinics in 15 European cities to evaluate the differences between some Northern countries regarding what foods, according to the patients, elicit hypersensitivity symptoms. Questionnaires concerning 86 different foods were administered to food-allergic individuals. The foods most often reported as eliciting symptoms in Russia, Estonia, and Lithuania were citrus fruits, chocolate, honey, apple, hazelnut, strawberry, fish, tomato, egg, and milk; which differed from the situation in Sweden and Denmark, where birch pollen-related foods, such as nuts, apple, pear, kiwi, stone fruits, and carrot were the most common reported culprits. The most common symptoms reported were oral allergy syndrome and urticaria. Birch pollen-related foods dominated as reported allergens in Scandinavia, whereas some mugwort-related foods were apparently of more importance in Russia and the Baltic States. Among 1 139 individuals, Grapefruit was the 18 (th)-most-often reported food allergen, purportedly resulting in adverse effects in 21%. (4)

A 3½-year-old boy is reported to have developed anaphylaxis after eating cashew nut, and later after eating a pectin-containing fruit ‘smoothie’. He was also reported to have a history of generalised pruritus after eating grapefruit. The child had skin-specific IgE for pectin, high levels of serum-specific IgE for cashew nut and pistachio, and low levels for grapefruit. The pectin in the smoothie was confirmed to be of citrus origin. The authors concluded that ingestion and inhalation of pectin can cause hypersensitivity reactions, and that allergy to cashew nut, and possibly pistachio, may be associated with pectin allergy. (9)

Other reactions

Grapefruit contains naringin, bergamottin and dihydroxybergamottin, which inhibit the protein isoform CYP3A4 in the intestine. It is via inhibition of this enzyme that grapefruit increases the effects of a variety of drugs. Therefore, the co-administration of certain drugs with grapefruit juice can markedly elevate drug bioavailability, and can alter the pharmacokinetic and pharmacodynamic parameters of the drugs. A single glass of the juice is usually sufficient to produce this interaction. (10-12)

No allergens from this plant have yet been characterised.

In a patient with anaphylaxis from mandarin (Citrus reticulata), a lipid transfer protein was isolated from mandarin fruit. Analysis of the patient's serum also demonstrated sensitisation to the lipid transfer protein Cit s 3, from orange, as well as to Cit s 1, a germin-like allergen. (13) Whether similar allergens occur in grapefruit, a closely-related family member, was not assessed.

Cross Reactivity

Cross-reactivity within the Rutaceae family (lemon, lime, orange, tangelo) can be expected, but has not been documented to date.

Latex allergy has been reported to be associated with allergy to a number of other foods, including avocado, banana, kiwi, papaya, chestnut, peach and grapefruit. (14) A 34-year-old female with asthma and atopic dermatitis who developed severe anaphylaxis to latex was described. She was shown to have serum-specific IgE directed against latex, banana, kiwi, grapefruit, and avocado. Skin-specific IgE was also detected to banana, grapefruit, avocado, and latex extract. (15)

Last reviewed : June 2022