Food allergy is a hypersensitive reaction experienced by some individuals to certain chemicals, mostly proteins, in some foods. Allergenic foods can be of plant or animal origin.  Even though, majority of food allergies occur after ingestion of allergenic food, there are reports that indicate that allergenic reactions can occur after physical contact with allergens-contaminated utensils, inhaling of vapors from allergenic food, and transfer of allergens from mothers to breast-feeding infants.

Allergic reaction occurs immediately (from with in minutes to an hour) or 6 – 24 hours after consumption (or contact with) of an allergenic food. Dosage of allergens capable of eliciting reactions varies greatly from an individual to an individual. However, even trace levels of allergens in the diet are capable of causing allergic reactions. Therefore, generally, allergic reactions are avoided by excluding foods known to contain allergens from ones diet.

Food allergens belong to a variety of protein families. The presence, content and variety of allergens differs among different foods. Below is a list of known allergenic proteins in plant food types, including cereals, fruits, vegetables, and nuts. 

Food type Allergen type
Nuts, other legumes and oil seeds
Peanut Ara h 1
Ara h 2
Ara h 3
Ara h 4
Ara h 5
Ara h 6 
Ara h 7 
Oleosin
31 kDa agglutinin
Cashew Ano o 1
English walnut Jug r 2
Jug r 1
Hazelnut Cor a 9
Cor a 8
Cor a 1.04
Cor a 4
Almond AMP
Brazil nut Ber e 1
Chestnut Cas s 5
Yellow mustard Sin a 1
Soybean Alpha-subunit of beta conglycinin
Glycinin subunits
P34/Gly m Bd 30K
Gly m 4
Gly m 3
20 kDa Kunitz trypsin inhibitor
Lentil Len c 1
Sesame Ses I 3
Ses I 2
Cereals
Barley Hor v 15 
Hor v 21
Rye Sec c 1
Sec c 20
Rice RAP (rice allergenic proteins)
Wheat Tri a 19
Tri a Bd 36K
Vegetables
Potato Beta-1,3-glucanases
Sola t 2
Sola t 3
Sola t 4
Sola t 1
Tomato Beta-1,3-glucanases
Lyc e 1
Lyc e 2
Bell pepper Cap a 1
Celery Api g 1
Api g 5
Api g 4
Asparagus Aspa o 1
Lettuce Lac s 1
Fruits
Kiwi Act c 1
Papaya Papain
Pineapple Bromelain
Ana c 1
Apple Mal d 2
Mal d 1
Mal d 4
Sweet cherry Pru av 1
Pru av 4
Pear Pyr c 6
Melon Cuc m 1/cucumisin
Banana Beta-1,3-glucanases
Avocado Pers a 1

Adapted from Breiteneder (2006)

References
Breiteneder, H. 2006. Classifying food alleregens. Pages 21 - 45. In Koppelman, S. J. and Hefle, S. L., eds. Detecting Allergens in Food. Woodhead Publishing Limited, Cambridge, UK.

Taylor, S. 2006. The nature of food allergy. Pages 3 - 17. In Koppelman, S. J. and Hefle, S. L., eds. Detecting Allergens in Food. Woodhead Publishing Limited, Cambridge, UK.

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