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Keywords:

  • asthma;
  • food allergy;
  • IgE;
  • ImmunoCAP;
  • rhinitis;
  • rice (Oryza sativa);
  • urticaria

Rice provides 25–80% of the daily calories consumed by more than 50% of the world population. Second to maize it is the most frequent cereal produced and accounts for 27.6% of the world production of cereals (1). Even though 520 million tons of rice are consumed worldwide every year, most reports describe an immunologically-mediated urticaria after contact with raw rice (2,3), whereas reports of immediate hypersensitivity reactions after ingestion of rice are scarce (4,5). Therefore, rice is commonly regarded as hypoallergenic and is frequently included in diets for allergic patients.

A 27-year-old woman without a history of atopy presented at the allergy unit because of several episodes of rhinitis with sneezing, itching of the scalp and asthma within minutes after eating meals with seafood and rice. With each episode the symptoms became stronger and the last reaction was accompanied by acute urticaria. Six months before the first reaction she spent several months in the Far East without experiencing any symptoms after consuming this kind of food.

Skin prick tests (SPT) with a battery of common inhalant (ALK, Hørsholm, Denmark) and food allergen extracts (Stallergènes, Antony Cédex, France), including different fishes, seafood and rice were all negative, however, ‘prick–prick’ and scratch tests were clearly positive with ‘native’ cooked rice. SPT with rice extract from another manufacturer (Bencard) elicited a positive wheal-and-flare reaction. The total IgE concentration was 55 kU/l, IgE specific to rice (CAP FEIA, Pharmacia) were 4.6 kU/l (CAP class 3), to oat 1.5 kU/l (CAP class 2), to wheat 0.9 kU/l (CAP class 2), to rye 0.7 kU/l (CAP class 2), to corn 0.56 kU/l (CAP class 1), to barley 0.36 kU/l (CAP class 1), to soy, buckwheat, fish and shrimps 0, respectively.

Based on the patient's history, the positive prick–prick tests and presence of IgE antibodies to rice, the diagnosis of food allergy to rice was made. The patient refused an oral provocation. She was advised to avoid further rice consumption and she received an emergency kit consisting of histamines, steroids and epinephrine. Eighteen months later she experienced an allergic reaction with rhinitis and asthma after a vegetarian meal consisting of tofu and rice, although she removed the rice from her plate. The concentration of IgE specific to rice was still increased (10.5 kU/l) (CAP class 3) while no IgE antibodies could be detected to soy. Under elimination diet the patient remained asymptomatic during two years and the level of IgE antibodies to rice dropped to 2.3 kU/l (CAP class 2). During travel in the USA she ate Chinese noodles without knowing that they were produced from rice. Immediately after ingestion of these noodles she developed generalized itching and dyspnea. After this allergic reaction the patient carefully avoided meals containing rice. Three years after the last episode IgE specific to rice has decreased strikingly to 0.5 kU/l (CAP class 1). The SPT to native cooked rice became negative.

Rice (Oryza sativa) belongs with other cultivated cereals to different tribes of the Poaceae family. As previously described (2,4), we also observed the presence of IgE specific to different cereals, but in lower concentrations than to rice. The existence of close allergenic cross-reactivity between different cereal grains has already been demonstrated by RAST inhibition studies (4,6). A 16-kDa rice protein (RP) was identified as a cross-reactive IgE binding structure that fulfilled the criterion of a major allergen (6). Recently, a 33-kDa rice allergen, designated Glb33, was identified as a novel plant glyoxalase I (7). Our patient had no problems when eating other cereals nor she suffered from hay fever to grass pollen. A study from Japan described cross-allergenicity between rice and buckwheat antigens (8), but IgE antibodies to buckwheat were not found in our patient. Müsken et al. (4) found similar allergenic potency of different sorts of rice all containing allergens of low molecular weight (14.4 and 28 kDa) as detected by western blotting.

In conclusion, our patient demonstrated that in a nonatopic person ingested rice can produce IgE-mediated allergic reactions and therefore should be regarded as a potential cause of food allergy. The strict avoidance over years may lead to loss of the sensitization.

References

  1. Top of page
  2. References
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Accepted for publication 9 November 2001