Rape seed

Further Reading

Rape w203

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Code: f316
Latin name: Brassica napus
Source material: Whole seeds
Family: Brassicaceae
Common names: Rape seed, Rapeseed, Canola, Oilseed Rape
Brassica napus is a quite variable species, with 3 important subspecies:
  • B. napus napobrassica (rutabagas or swedes)
  • B. napus pabularia (Siberian kale, Hanover salad, etc.)
  • B. napus oleifera (Rape seed)

Allergen Exposure

Geographical distribution
Rape is an annual plant similar to the turnip and rutabaga. It is thought that Brassica napus originated from a hybridisation between the turnip (B. rapa) and kale (B. oleracea acephala). Rape originated in northern Europe and was cultivated near the Mediterranean Sea, but is now grown throughout the world. Canola, a selectively bred variant of Rape, was developed in the late 1970s in Canada as a more nutritious source of vegetable oil than Rape seed.

The Rape plant is an annual or biennial growing up to 1.2 m, with yellow flowers that in their season make Rape fields a striking sight. At the same time, the released volatile organic compounds (there are 22 altogether (1)) create a distinct smell. The slick, turnip-like flat leaves are 10 to 30 cm long. Unlike turnip, Rape has no swollen root, only a thin taproot. Sickle-shaped pods containing tiny round seeds are produced.

This plant has become a very common crop in the UK and elsewhere. Rape is generally grown in large fields for green livestock fodder, birdseed or Rape seed oil.

Canola is a new type of Rape grown commercially for the seed, which is lower in saturated fats and fatty acids than the original cultivar. Canola oil is also almost free of erucic acid, a toxic compound plentiful in older varieties.

Unexpected exposure
Canola oil has become a common ingredient in both homemade and commercial foods. 

Rape seed contains 2 main storage proteins, a high-molecular-mass legumin-like 12 S globulin and a low-molecular-mass 2 S protein (also known as napin or nIII) (2-4,6, 9).

The 2 S protein has been characterised as the following:

  • Bra n 1, a 2S albumin (napin); the protein consists of 2 different chains of 9.5 and 4.5 kDa (5-12).

In a study to identify possible major allergens in Rape seed and Turnip rape using sera from 72 atopic children with positive SPT to these proteins, major reactivity was demonstrated to a group of homologous, approximately 9.5 to 14.5 kDa proteins that were identified as 2S albumins (napins). Approximately 80% of the patients had IgE antibodies to purified napins from both plants. In SPT using purified napins, positive reactions were demonstrated in all 6 children tested (12).

Rape seed is able to generate chitinase when wounded, as demonstrated by a study in which complementary and genomic DNA strands coding for a Brassica napus chitinase have been cloned and sequenced (13-14). The allergenic potential of this protein is not known to date.

Low-molecular-mass trypsin isoinhibitors have been isolated (but their antigenicity is unknown) (15).

A 2S albumin recombinant protein from the seeds of Brassica napus was shown to have a high thermal stability, and these results suggest that rproBnIb, like other 2S albumins, may be able to reach the gut immune system intact (11).

Potential cross-reactivity

An extensive cross-reactivity among the different individual species of the family could be expected to occur clinically with Rape seed (16). A study of children sensitised to Rape seed reported that the high correlation in the skin reactivity between Rape seed and Turnip rape suggested cross-reactivity, and this is supported by the fact that they both contain homologous 2S albumins (17).

The 2S albumin storage protein in Rape seed exhibits extensive sequence similarity with 2S albumins from other seeds. Cross-reactivity between Mustard and Rape seed flours as a result of this protein has been reported (6). Similarly, the Mustard allergen Sin a 1 was found to be related to other low-molecular-mass albumins, such as those isolated from Rape seed, Castor bean and Brazil nut. Structural similarity was also reported between the glutamine-rich large chain of Sin a I and a proline-rich zein, a gliadin, and trypsin and alpha-amylase inhibitors isolated from the seeds of several monocotyledons (18).

Clinical Experience

IgE-mediated reactions
Rape seed protein may induce symptoms of allergy in sensitised individuals, predominantly in occupational settings such as animal feed factories, grain mills and farms. Individuals may be sensitised to either Rape seed as a food or Rape seed pollen as an inhalant. For allergy to the pollen, see Rape w203.

A 48-year-old man who had been working in a feed processing plant suffered episodes of wheezing with shortness of breath after exposure to Rape seed flour. After 5 years of exposure, he noted sneezing and rhinorrhoea whenever the flour was being discharged from the mill and he was in the vicinity. Symptoms subsided 2 hours after the exposure ended. He also developed oedema and pruritis of the lips, oral mucosa and pharynx, and facial urticaria immediately after ingestion of a small amount of Mustard sauce. The reactions were attributed to cross-reactivity with the 2S albumin allergen from Rape seed flour and Sin a 1 from Mustard (6).

A 48-year-old man, employed in a grain and animal feed store for 9 years, reported rhinorrhea, sneezing, nasal obstruction, ocular burning, coughing and wheezing, which had all occurred over the previous 12 months and were induced by Rape flour (19).

A 43-year-old male working in the grain industry experienced cough and chest tightness during working hours. SPT was positive to Rape extract. A broncho-provocation test was positive. The study results confirmed that the inhalation of Rape dust, not pollen, was the cause of his IgE-mediated occupational asthma (20). Similarly, a study demonstrated that inhalation of Rape flour caused bronchoconstriction, induced an eosinophilic inflammatory bronchial response, and increased bronchial hyperresponsiveness in sensitised asthmatic farmers. Contact with the allergen took place through its presence as flour in animal fodder (21).

In a Finnish study, skin prick testing for suspected food allergy in young children with atopic dermatitis frequently found positive reactions with Turnip rape and Rape seed. A subsequent study of 1,887 Finnish children, who were screened with SPT for sensitisation to Turnip rape and Rape, found that 206 (10.9%) had reactivity for Turnip rape and/or Rape seed (9.3% for Turnip rape and 9.4% for Rape seed). Twenty-five (89%) of 28 children enrolled in the challenge study showed a positive challenge reaction to Turnip rape. Seventeen reacted with labial whealing after labial challenge, and 8 had facial urticaria, flare-up of atopic dermatitis or abdominal symptoms after oral challenge. One child developed rhinitis. Four children had immediate symptoms within 3 hours, and 4 experienced delayed reactions. Allergen-specific IgE determination for Turnip was positive in 17 of those positive to labial challenge. Three challenge-positive children showed a flare up of atopic dermatitis when the oral challenge had lasted for 2-5 days. The high correlation in skin reactivity between Rape seed and Turnip rape suggested cross-reactivity, and this is supported by the fact that both substances contain homologous 2S albumins (17).

In a subsequent study, 64 of these children, with atopic dermatitis and the presence of skin reactivity IgE to Turnip rape and/or Oilseed rape, were assessed for any common sensitisation pattern to certain foods or pollens, and were shown to have significantly more prevalent skin- and serum-specific sensitisation to various foods (Cow's milk, Egg, Wheat, Mustard) and pollens (Birch, Timothy, Mugwort) than a control group (22).

Other reactions
Pure Rape seed oil is reported not to cause allergic reactions (23). However, occupational allergic contact dermatitis from PEG-4 Rape seed amide in massage oil has been reported (24).

In the 1980s, Spanish toxic oil syndrome occurred as a result of the presence of aniline as a permitted adulterant for imported French Rape seed oil; this caused disease in 20,000 people and over 2,500 deaths. The toxic oil syndrome was a multisystemic disease brought on by the ingestion of Rape seed oil denatured with 2% aniline (25-26).

Compiled by Dr Harris Steinman, harris@zingsolutions.com


  1. Butcher RD, Macfarlane Smith W, Robertson GW, Griffiths DW. The identification of potential aeroallergen/irritant(s) from oilseed rape (Brassica napus spp. Oleifera): volatile organic compounds emitted. Clin Exp Allergy 1994;24:1105-14
  2. Schwenke KD. Structural studies on native and chemically modified storage proteins from rapeseed (Brassica napus L.) and related plant proteins.
    Nahrung 1990;34(3):225-40
  3. Inquello V, Raymond J, Azanza JL. Disulfide interchange reactions in 11S globulin subunits of Cruciferae seeds. Relationships to gene families.
    Eur J Biochem 1993;217(3):891-5
  4. Sjodahl S, Rodin J, Rask L. Characterization of the 12S globulin complex of Brassica napus. Evolutionary relationship to other 11-12S storage globulins.
    Eur J Biochem 1991;196(3):617-21
  5. Palomares O, Monsalve RI, Rodriguez R, Villalba M. Recombinant pronapin precursor produced in Pichia pastoris displays structural and immunologic equivalent properties to its mature product isolated from rapeseed.
    Eur J Biochem 2002;269(10):2538-45
  6. Monsalve RI, Gonzalez de la Pena MA, Lopez-Otin C, Fiandor A, et al. Detection, isolation and complete amino acid sequence of an aeroallergenic protein from rapeseed flour. Clin Exp Allergy 1997;27(7):833-41
  7. Monsalve RI, Villalba M, Lopez-Otin C, Rodriguez R. Structural analysis of the small chain of the 2S albumin, napin nIII, from rapeseed. Chemical and spectroscopic evidence of an intramolecular bond formation. Biochim Biophys Acta 1991;1078(2):265-72
  8. Pantoja-Uceda D, Bruix M, Santoro J, Rico M, Monsalve R, Villalba M. Solution structure of allergenic 2 S albumins.
    Biochem Soc Trans 2001;30(6):919-24
  9. Monsalve RI, Lopez-Otin C, Villalba M, Rodriguez R. A new distinct group of 2 S albumins from rapeseed. Amino acid sequence of two low molecular weight napins. FEBS Lett 1991;295(1-3):207-10
  10. Schmidt I, Renard D, Rondeau D, Richomme P, Popineau Y, Axelos MA. Detailed physicochemical characterization of the 2S storage protein from rape (Brassica napus L.).
    J Agric Food Chem 2004;52(19):5995-6001
  11. Pantoja-Uceda D, Palomares O, Bruix M, Villalba M, Rodriguez R, Rico M, Santoro J. Solution structure and stability against digestion of rproBnIb, a recombinant 2S albumin from rapeseed: relationship to its allergenic properties.
    Biochemistry 2004;43(51):16036-45
  12. Puumalainen TJ, Poikonen S, Kotovuori A, Vaali K, Kalkkinen N, Reunala T, Turjanmaa K, Palosuo T. Napins, 2S albumins, are major allergens in oilseed rape and turnip rape.
    J Allergy Clin Immunol 2006;117(2):426-32
  13. Hamel F, Bellemare G. Characterization of a class I chitinase gene and of wound-inducible, root and flower-specific chitinase expression in Brassica napus. Biochim Biophys Acta 1995;1263(3):212-20
  14. Rasmussen U, Bojsen K, Collinge DB. Cloning and characterization of a pathogen-induced chitinase in Brassica napus.
    Plant Mol Biol 1992;20(2):277-87
  15. Ascenzi P, Ruoppolo M, Amoresano A, Pucci P, Consonni R, Zetta L, Pascarella S, Bortolotti F, Menegatti E. Characterization of low-molecular-mass trypsin isoinhibitors from oil-rape (Brassica napus var. oleifera) seed.
    Eur J Biochem 1999;261(1):275-84
  16. Yman L. Botanical relations and immuno-logical cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09
  17. Poikonen S, Puumalainen TJ, Kautiainen H, Burri P, Palosuo T, Reunala T, Turjanmaa K. Turnip rape and oilseed rape are new potential food allergens in children with atopic dermatitis. Allergy 2006;61(1):124-7
  18. Menendez-Arias L, Moneo I, Dominguez J, Rodriguez R. Primary structure of the major allergen of yellow mustard (Sinapis alba L.) seed, Sin a I.
    Eur J Biochem 1988;177:159-66
  19. Di Giacomo GR, Boschetto P, et al. Asthma and rhinoconjunctivitis caused by rape flour: description of a clinical case. [Italian] Med Lav 1998;89(3):226-31
  20. Suh CH, Park HS, Nahm DH, Kim HY. Oilseed rape allergy presented as occupational asthma in the grain industry. Clin Exp Allergy 1998;28(9):1159-63
  21. Alvarez MJ, Estrada JL, Gozalo F, Fernandez-Rojo F, Barber D. Oilseed rape flour: another allergen causing occupational asthma among farmers. Allergy 2001;56(2):185-8
  22. Poikonen S, Puumalainen TJ, Kautiainen H, Palosuo T, Reunala T, Turjanmaa K. Sensitization to turnip rape and oilseed rape in children with atopic dermatitis: a case-control study. Pediatr Allergy Immunol 2008 Jan 22; [Epub ahead of print]
  23. Gylling H. Rape seed oil does not cause allergic reactions. Allergy 2006;61(7):895
  24. Isaksson M. Occupational allergic contact dermatitis from PEG-4 rapeseed amide in a massage oil.
    Contact Dermatitis 2002;47(3):175-6
  25. Diggle GE. The toxic oil syndrome: 20 years on. Int J Clin Pract. 2001;55(6):371-5
  26. Martín-Arribas MC, Izquierdo Martínez M,
    de Andrés Copa P, Ferrari Arroyo MJ,
    Posada de la Paz M. Characteristics of disability and handicap among Toxic Oil Syndrome (TOS) cohort patients: a cross-sectional study, 17 years after the original food intoxication.
    Disabil Rehabil 2003;25(20):1158-67

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.