Apples can be classified into four main groups: dessert, culinary, cider and ornamental. Apples are widely used and variable in type.

Apples are one of the most widely grown fruits in the western hemisphere. Early cultivation probably predates written history and over 1000 varieties exist. These varieties are usually grouped into summer and late-fall according to the time of maturity. L form of malic acid present in apples, pears and other temperate fruits. Allergens are heat unstable and pulp allergens are unstable in solution.

Apples are eaten fresh, are a chief ingredient of many desserts (e.g., baked apples, apple pie, and apple strudel). They are also processed into dried apples, tinned sauce and slices, pasteurised juice, and vinegar. They are also fermented into Drinks (alcoholic) like cider, and apple brandies, such as calvados.

Apple contains over 266 volatile components that include alcohol, esters, aldehydes, ketones, ethers, acids, bases, acetals, and hydrocarbons. (Dimick 1983 ref.1130 8)

Allergens/Function:

Allergens:
Major: Mal d 1, a 17 kDa, heat labile, Bet v 1-homologue. A PR 10 plant protection protein.
Mal d 2, a 31 kDa, thaumatin-like protein
Minor: Mal d 3, a 9 kDa protein, a Lipid Transfer Protein.
Major: Mal d 4, a 14 kDa protein

a Bet v 6-related food allergen - PCBER - has been detected. (Karamloo 2001 ref.6910 3)

18 and 31 kd allergens, which are heat labile and unstable in solution. The major allergen is named Mal d 1. Also contains the Mal d 2 allergen, a thaumatin-like protein, and Mal d 3, a lipid transfer protein (LPT). (Rodriquez) Almost complete elimination of allergenic potency is achieved by short heating processes. (Paschke 2001 ref.4018 8)

Different Mal d 1 isoforms can be present within a single cultivar (Son 2000 ref.3532) The authors conclude that divergent allergenicity of apple strains mainly depends on different expression levels of the major allergen. Introduction of a proline residue in position 111 of Mal d 1 and in position 112 of Bet v 1 led to a drastic reduction of allergenicity of both the pollen and the food allergen, obviously also removing the cross-reactive epitope. (Son 1999 ref.6126 3)

The level of allergen (protein) varies with the type (species) of apple and its maturity (ripeness). (Vieths) (Hsieh 1995 ref.1133 8) Golden Delicious apples had the greatest amount of the 18 kd allergen (compared with McIntosh, Red Delicious, Granny Smith). Level of 18 kd allergen in Golden Delicious > Boskoop > Jamba (Vieths). This also explains the different skin prick reactions to allergens from the different extracts. (de Groot 1996 ref.1411 8)

Apples in stores had higher levels of allergen than freshly picked fruit. The amount of 18 kd allergen increased significantly when apples were stored at 4 degrees C, but not under controlled atmospheric conditions of oxygen and carbon dioxide. (Hsieh 1995 ref.1133 8)

Analysis of the heat stability of lipid transfer protein from apple. (Asero 2003 ref.8680 3)

Adverse Reactions:

IGE AND IMMUNE:
Allergic reactions: Rhinitis, itching and tingling and other mild reactions on the oropharyngeal mucosa are the most common complaints after eating raw apples, and angioedema, urticaria and shock are less common.

Allergy reactions. Oral Allergy Syndrome (Helbling), also from kissing (Wuthrich 1997 ref.692 89). Rhinoconjunctivitis. Asthma. Laryngeal oedema. Angioedema. Hand swelling. Pruritis. Wheezing. Hypotension. Conjunctivitis. Dizziness. Dyspnea.

Apple-dependant food-dependant exercise-induced anaphylaxis. (Anibarro 1994 ref.469 91) (Guinnepain 1996 ref.823 12) (Anaut 1994 ref.6605 8) A study reports on 7 cases of food-dependant exercise induced-anaphylaxis. The responsible foods were wheat (2 cases), corn, barley, shrimp, apple, paprika and mustard. (Mathelier-Fusade 2002 ref. 7125 2)

Contact urticaria. (Meynadier 1982 ref.1551 8)

Itching and tingling with or without oedema of the lips, mouth and tongue were the most common complaints after eating raw fruits and vegetables. In addition, laryngeal and abdominal disturbances, rhinitis and hand dermatitis were recorded. (Hannuksela)

24% of 276 adult patients reported asthma or rhinitis symptoms on eating or handling various foods, of which hazel nut, apple and shell fish were the most often named. (Eriksson)

'Apple contact urticaria syndrome' - rhinitis, itching and tingling and other mild reactions on the oropharyngeal mucosa are the most common complaints after eating raw apples. (Kremser 1983 ref.1131 8) Oral allergy syndrome. (Ortolani)

Apple allergy is found in approximately 50% of patients with immediate hypersensitivity to birch pollen. In Hokkaido 20% of birch pollinosis patients were hypersensitive to apple pulp. (Yamamoto 1993 ref.1485 8) However, allergy to Rosaceae fruits in patients without a related pollen allergy is also a severe clinical entity. Profilin- and Bet v 1-related structures are not involved. (Fernandez 1993 ref.1270 8) (Van Ree 1995 ref.102 89)

Crossreactive.

Itching and tingling of the lips and mouth with severe oedema of the lips and tongue, irritation of the throat and slight colic, nausea and vomiting (Sakamoto 1989 ref.1124 8)

The acidity of apple juice may result in bronchoconstriction in some individuals. (Santucci 1990 ref.1121 8)

Patients who are birch pollen- and apple-allergic improve if desensitised to birch pollen. (Herrmann 1995 ref.1132 8)

Apple is considered a common cause of gastrointestinal allergy and aphthous stomatitis.

The prevalence in the Netherlands of atopy caused by apple, peach, and hazelnut in patients with tree pollinosis was evaluated. Skin prick tests for apple, peach, and hazelnut were positive in 51 (64.6%), 61 (77.2%), and 71 (89.9%) patients, respectively. Granny Smith showed more positive skin reactions and a better agreement with clinical history than Golden Delicious. RAST for apple, peach, and hazelnut was positive in 53 (68.8%), 13 (16.9%), and 31 (40.3%) patients, respectively. (de Groot 1996 ref.1411 8)

In a study of 99 children with atopic dermatitis, hen egg was the most common food allergen in children under 1 year of age. After that age, apple, carrot, pea, and soybean elicited positive reactions as often as egg (Hannuksela).

In 40 birch pollen-allergic patients, dose-dependent histamine release was demonstrated to apple peel = apple pulp > peach = cherry. (Kleine 1992 ref.1362 8)

A significant association exists between recurrent serous otitis media and food allergy was demonstrated in 81 of 104 patients. An elimination diet resulted in a significant amelioration of the disease in 86% of the patients and a challenge diet provoked recurrence of symptoms in 94%. The highest frequency was seen with milk, wheat, egg, peanut, soy and corn, and <10% were seen with orange, tomato, chicken and apple. (Nsouli 1994 ref.7725 6)

This study reports on two patients with apple-dependent exercise-induced anaphylaxis. (Sanchez 2003 ref.8567 4)

NON IMMUNE:
Some children may not be able to tolerate even low doses of fructose (see), resulting in diarrhoea. Also, excess ingestion may result in a 'sugar load' resulting in diarrhoea. Hoekstra et al found that clear apple juice was more potent in causing chronic non-specific diarrhoea (CNSD) than cloudy apple juice was.

A report by Martin et al of a jejunal bezoar caused by a piece of apple peel (letter).