Route Of Exposure

Apricot is a species of Prunus, classified with the plum in the subgenus Prunus. It most probably originated in northern and western China and Central Asia. It now thrives in most temperate climates, and ranks fifth in worldwide deciduous fruit production.

The apricot tree grows 8 to 12 m in height. The leaves are ovate, 5-9 cm long and 4-8 cm wide, with a rounded base, a pointed tip and a finely serrated margin. The flowers are 2-4.5 cm in diameter, with 5 white-to-pinkish petals; they are produced singly or in pairs in early spring, before the leaves.

The apricot fruit is a drupe similar to its relative, peach, but smaller, 1.5-2.5 cm in diameter (larger in some modern cultivars). Apricot ranges in colour from pale yellow to brilliant orange, often tinged red on the side most exposed to the sun; its surface is usually pubescent. The oval single seed (pit) is enclosed in a hard stony shell, often called a ‘stone’, with a grainy, smooth texture, except for 3 ridges running down the same side; the stone falls out easily when the fruit is halved. There are many varieties of apricot.

Apricot is sold fresh, canned or dried. Dried apricots are usually treated with sulphur dioxide to preserve their colour and to prevent spoilage.

A green dye can be obtained from the leaves and the fruit. The durable and handsome wood is used for tools. The kernels are poisonous until roasted, since they have high concentrations of cyanogenic glycosides, which are found in most stone fruit seeds, bark, and leaves. But the roasted pits are used in confections and to flavour liqueurs. An edible gum is obtained from the apricot tree trunk. The oil may be used in perfumery, cosmetics and pharmaceuticals.

Clinical Relevance

Allergen description

The following allergens have been characterised:

Lipid transfer proteins concentrate in the pericarp (skin) of the fruit, whereas the pulp contains lower amounts of this allergen.

Potential Cross Reactivity

An extensive cross-reactivity among the different individual species of the Rosaceae family (almond, apple, apricot, peach, etc.), and more specifically of the genus Rubus (cloudberry, dewberry, raspberry), could be expected, but this has not been documented as yet. Although extensive cross-reactivity among the family members may occur, it will be dependent on the specific allergens present and the individual’s sensitisation to those allergens. This is illustrated by a study of 34 adult patients complaining of adverse reactions to Rosaceae, of whom 26 and 24, respectively, were shown to have skin- and serum-specific IgE directed at Rosaceae. No evidence of clinical reactivity was found in 66% of positive skin-prick tests or 63% of positive specific-IgE determinations to fruits. A total of 226 food challenges was performed; most reactions were caused by peach (22 patients), apple, and apricot. Ten patients (46%) were clinically allergic to peach and other Rosaceae. The authors concluded that positive skin- and serum-specific IgE tests should not be taken as the only guide for multi-species dietary restrictions, yet potential clinical allergy to other Rosaceae should not be neglected.

Panallergens present in apricot may result in variable degrees of cross-reactivity with other foods and plants containing these panallergens.

The major allergen Pru ar 1 from apricot, along with the major allergens in apple (Mal d1), pear (Pyr c 1) and sweet cherry (Pru av 1), is a structural homologue of the birch pollen major allergen Bet v 1, and may result in cross-reactivity with these and other plants and foods containing this panallergen.

Apricot lipid transfer protein (LTP), Pru ar 3, has a sequence amino acid identity of 91% and 94% with peach and almond LTPs, respectively, and is therefore highly cross-reactive. Apricot and peach LTPs have a very similar structure to maize LTP. Cherry LTP has a high amino acid sequence identity with the LTP from apricot, Pru ar 3 (86%), as well as with that of peach (Pru p 3, 88%), and maize (Zea m 14, 59%). Other foods that contain LTP include blueberry, peanut, walnut, pistachio, broccoli, carrot, celery, tomato, melon, kiwi and lettuce; this LTP may contribute to severe systemic reactions. The LTPs of Rosaceae fruits, in particular peach, are major allergens for Mediterranean and southern Europe populations, where LTP allergens play a large contributory role in adverse effects, mostly systemic, compared to northern or central Europe, where Bet v 1 homologues and profilin play a greater role, resulting mainly in oral allergy syndrome. However, the IgE-binding cross-reactivity due to fruit lipid transfer protein has varying degrees of clinical relevance, and this cross-reactivity is not necessarily accompanied by cross-allergenicity to the corresponding fruits.

Cross-reactivity with latex has been suspected. In 137 patients with latex allergy and food allergy diagnosed by a convincing history of possible IgE-mediated symptoms occurring within 60 minutes of ingestion, 49 potential allergic reactions to foods were identified in 29 patients. Foods responsible for these reactions included banana in 9 patients (18.3%), avocado in 8 (16.3%), shellfish in 6 (12.2%), fish in 4 (8.1%), kiwi in 6 (12.2%), tomato in 3 (6.1%), watermelon, peach, and carrot in 2 (4.1%) each, and apple, chestnut, cherry, coconut, apricot, strawberry, and loquat in 1 (2.0%) each. Importantly, as suggested in a study of 2 children with latex hypersensitivity, skin-prick tests with fruit (including apricot) may be positive, but no symptoms might result after ingestion.

Therefore, elimination diets requiring avoidance of all foods containing a panallergen, or relying only on the results of allergy testing, might result in unnecessary restriction of food.

Clinical Experience

IgE-mediated reactions

Apricot may result in allergic reactions, ranging from mild symptoms such as oral allergy syndrome, to severe systemic reactions such as anaphylaxis.

Allergy to apricot and other Rosaceae fruit, in patients without a related pollen allergy, is often a severe clinical entity and occurs more commonly in Mediterranean and other southern European patients. A lipid transfer protein allergen is often implicated. Profilin- and Bet v 1-related structures are not involved. Rosaceae fruit allergy is frequently associated with birch pollinosis in central and northern Europe, and with grass pollen allergy in central Spain. The main cross-reactive structures involved for birch pollen allergy are Bet v 1 and profiling; for grass pollinosis they are profilin and carbohydrate determinants. In a study of 11 patients from central Spain allergic to Rosaceae fruit (apple, peach, and/or pear) but not to pollen, who were compared with 22 control subjects with combined grass pollen and fruit allergy, symptoms were reported to be severe in the former group, with 82% of patients reporting systemic symptoms, mainly anaphylaxis (73%), whereas oral symptoms were less frequent (64%). Anaphylactic shock was observed in 36% of patients. The fruit allergens involved showed cross-reactivity among Rosaceae species but were not related to profilin or Bet v 1. Ninety-one per cent of patients with combined grass pollinosis and fruit allergy reported oral allergy, 45% reported systemic symptoms, 18% reported anaphylaxis, and 9% reported anaphylactic shock.

Similarly, 30 Italian patients, all with oral allergy syndrome (2 with systemic reactions) to apricot, were investigated with food challenges, skin-prick tests and serum-specific IgE antibody tests to apricot. All sera recognised an LTP, whereas other detected allergens were minor allergens.

A study was conducted at 17 clinics in 15 European cities to evaluate the differences among some northern countries regarding what foods, according to patients, elicit hypersensitivity symptoms. It was reported, on the basis of questionnaires completed by food-allergic individuals concerning 86 different foods, that the foods believed to elicit symptoms most often in Russia, Estonia, and Lithuania were citrus fruits, chocolate, honey, apple, hazelnut, strawberry, fish, tomato, egg, and milk; a profile that differed from Sweden and Denmark, where birch pollen-related foods, such as nuts, apple, pear, kiwi, stone fruits, and carrot were the most common perceived causes. The most common symptoms reported were oral allergy syndrome and urticaria. Birch pollen-related food allergens seemed to dominate in Scandinavia, whereas some mugwort-related foods were apparently of more importance in Russia and the Baltic states. Among 1 139 individuals, apricot was the 27 (th)-most-reported allergenic food, resulting in adverse effects in 18%.

A number of case studies illustrate the clinical effects of allergy to apricot.

A 39-year-old female described the onset of acute urticaria, angioedema, shortness of breath, wheezing and dry cough after eating mulberry for the first time. She described reactions which had previously occurred after eating white grape and, on another occasion, white grape and apricot. Reactions were life-threatening, requiring emergency-room visits. Serum-specific IgE was 0.59 for apricot and 1.15 kU/L for grape.

In a study aimed at characterising raspberry allergens, a 44-year-old patient was described who had experienced oral allergy syndrome to apple, facial angioedema from peach, and anaphylaxis to apricot. Prick-to-prick tests were positive to apple, peach, cherry, and apricot.

A study described a 21-year-old woman who developed primarily airborne sensitisation to LTP of peach, with symptoms of severe perennial rhinitis, 6 months after starting work in a wholesale fruit storehouse in southern Italy, where large amounts of fruits, including peach, were handled. Symptoms subsided when she left the workplace for more than 5 days, and relapsed as soon as she was back at work. She subsequently developed severe food allergies to peach, hazelnut, peanut, apricot, plum and tomato.

Authors have suggested that in birch pollen-allergic patients with allergy to Rosaceae fruit, skin-prick tests with fresh food remain the most reliable method of diagnosing food hypersensitivity. In contrast, in patients not allergic to birch pollen but with allergy to Rosaceae fruit, the most reliable strategy for detection of LTP sensitivity is skin-prick testing with properly prepared fruit peel extracts. However, with the advent of representative recombinant LTP allergens, serum-specific IgE evaluation may contribute to the diagnosis of allergy to apricot.

Other reactions

Contact urticaria to apricot stone has been described.

Intestinal obstruction in a 16-month-old boy as a result of the ingestion of whole dried apricot has been reported. Apricot had been eaten several hours earlier and had swelled in the intestinal lumen.

Sulphur dioxide and other sulphite preservatives, used to preserve dried apricot, may result in respiratory and other adverse reactions.

Cyanogenic glycosides are present in apricot seed (kernel). A 41-year-old woman became weak and dyspnoeic within 20 minutes of ingestion of apricot kernels purchased at a health food store. The patient was comatose and hypothermic on presentation but responded promptly to antidotal therapy for cyanide poisoning.