Rapeseed
Summary
Rapeseed is part of the Brassicaceae family and is an important source of edible oil worldwide. While the refining process for this oil should result in the removal of all allergens, Bra n 1, the major allergen present in rapeseed, is not always destroyed and could cause allergy via ingestion. Despite this, no clinical instances of allergy have occurred through ingestion of rapeseed oil, with reactions being limited to positive skin prick testing in sensitized individuals. Although rare, clinical reports of IgE-mediated reaction to inhaled rapeseed allergens have been reported to cause respiratory issues in exposed occupational workers.
Route Of Exposure
Main
Ingestion
Other topics
Inhalation as rapeseed dust.
Clinical Relevance
The majority of rapeseed is consumed as oil, available as cold-pressed or refined oil. Refining oils should result in the near-complete removal of proteins responsible for allergic reactions, therefore preventing allergic reactions upon ingestion. However, the major allergens present in rapeseed are reported to be extremely resistant to pepsin digestion and denaturation, and are therefore not destroyed during conventional food processing. During the manufacture of cold-pressed oils some protein from the seeds may remain. Therefore, allergic reaction to some rapeseed oils remains a possibility. However to date, no clinical evidence of allergic reactions following the ingestion of rapeseed oil has been reported. Evidence of sensitization based upon skin prick testing results has been observed in clinical studies.
Allergic rhinitis
In a study assessing sensitization rates covering 20 years to weed pollens in 6,220 patients with suspected allergic rhinitis or bronchial asthma, 20.4% of those undergoing a skin prick test to rapeseed (362/1,771) were positive for the first decade from 1998-2007. This increased further to 31.3% (431/1,378) during the second decade, from 2008-2017.
Asthma
Clinical cases of allergy from inhaled rapeseed allergens are limited. One study assessed 3 farmers with occupational asthma who had positive skin prick tests and serum specific IgE levels towards rapeseed extract. The farmers also had positive bronchial provocation tests to rapeseed allergen extract, suggesting that rapeseed, when used in animal fodder, can be a cause of occupational allergy in farmers. An earlier study also reported that inhalation of oilseed rape dust caused IgE-mediated bronchoconstriction in an exposed worker of the grain industry.
Cross-Reactivity
Cross-reactivity between different foods within the Brassicaceae family have been reported, especially with mustard seeds. An IgE and IgG cross-reactivity between rapeseed and mustard allergens (2S albumins) were present in a rapeseed allergic patient. Despite this, clinical cases of cross reactivity involving rapeseed are limited.
A study of 1,887 Finnish children with atopic dermatitis found that 11 % (206/1887) had positive skin prick tests to rapeseed. However, none of the children had clinical manifestations such as immediate or delayed symptoms from this sensitization. A subsequent study found that French children with atopic dermatitis and skin prick positive to turnip rape or rapeseed were polysensitized to various foods and pollens. These reactive children frequently had associated asthma (36 %) and allergic rhinitis (44 %).
References
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