Thank you for your inquiry.
Before directly answering your question, I would like to point out that there are many allergens in wheat, gliadin being only one of these. The water-soluble albumins and globulins also have been responsible for allergic reactions including “baker’s asthma,” and have also caused allergic reactions upon ingestion.
There is well-recognized allergenic cross-reactivity between grains, including barley and wheat. This cross-reactivity extends to allergens other than gliadin. I have copied below some references (including two of the abstracts) which have investigated this cross-reactivity between grains, with an emphasis on the cross-reactivities demonstrated between barley and other grains.
Thus, although not all patients who are allergic to one grain will be allergic to others, there is clear potential for this to occur not only to the gliadin portion but to other allergens within wheat and other grains as well. Normally, if a patient has been eating a grain without difficulty, I would not suggest removal of that grain from the diet. I would only suggest that the patient not ingest the grain to which the reaction occurred. However, if the patient had not been eating other grains, because of the potential of cross-reactivity, I would suggest that they not do so until which time one could demonstrate negative testing for a specific IgE to that grain and after which an in-office oral challenge had been done.
In the case of your patient, at least at face value, their reaction occurred to barley. I would not on this basis ask your patient to avoid other grain products that they have eaten previously without difficulty, but if they had not eaten these grain products, as noted, I would suggest they be evaluated as described above before doing so. Thus, if the reaction had been to wheat, I would treat other grains in the same fashion.
Thank you again for your inquiry and we hope this response is helpful to you.
Hypersensitivity to Inhaled Flour Allergens Comparison between Cereals
B. A. Baldo
Volume 35, Issue 1, pages 45–56, January 1980
Radioallergosorbent testing (RAST) of sera from subjects sensitized to wheat and rye Hour indicated that there is significant reaction with seed extracts of 12 cereals (wheat, durum wheat, triticale, cereal rye, barley, rye grass, oats, canary grass, rice, maize, sorghum and Johnson grass). Results were evaluated in terms of taxonomic relationships and of the electrophoretically determined protein composition of the cereal extracts. RAST uptakes were uniformly low in sera from four rhinitic bakers, yet were significantly above the levels for non-allergic and cord sera. Much higher RAST uptakes were obtained with sera from four asthmatic bakers when tested with wheat and its close relatives, but there was still reasonably high reactivity with more distantly related cereals. RAST inhibition experiments indicated in a more direct way the extent of cross-reactivity between grain extracts of wheat, rye, barley and oats. One baker had a history of more severe attacks of breathlessness following inhalation of rye flour compared with wheat Hour. This was confirmed by bronchial challenge testing, but the comparison was not obviously consistent with the results of prick testing or estimation of histamine released from his leucocytes. The results as a whole suggested that the bran layers of cereal grains are at least as allergenic as flour.
Identification of crossreacting wheat, rye, barley and soya flour allergens using sera from individuals with wheat-induced asthma
C. P. SANDIFORD
Clinical & Experimental Allergy
Volume 25, Issue 4, pages 340–349, April 1995
We have conducted radio allergosorbent test (RAST), competitive RAST inhibition, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting using sera from patients with wheat-induced asthma to investigate the immunological relationship between wheat, rye, barley and soya, and to identify common proteins between these flours. RAST showed strong associations between the levels of specific IgE to wheat flour and those of rye and barley flour. Competitive RAST inhibition showed that wheat, rye, barley and soya flours contained crossreacting proteins, in decreasing concentrations. Wheat, rye and barley flours had similar protein profiles on gel electrophoresis. Soya flour contained a number of high molecular weight proteins not present in the other cereals. Western blotting using sera from 21 wheat flour hypersensitive individuals identified a large number of allergens in the different flours. Proteins of 69, 33, 26, 21 and 12 kDa were identified as major wheat flour allergens. Rye flour proteins of 21 and 12 kDa, and barley flour proteins of 69, 52 and 10 kDa were the major allergens identified by serum from wheat hypersensitive individuals. The major common protein of soya and wheat flour had a molecular weight of 21 kDa. The majority of crossreacting allergens identified between the different flours have molecular weights similar to those of known flour enzymes or enzyme inhibitors.
1. Block G, Tse KS, Kijek K, Chan H, Chan-Yeung M. Baker's asthma. Studies of the cross-antigenicity between different cereal grains. Clin Allergy 1984;14(2):177-85.
2. Guenard-Bilbault L, Kanny G, Moneret-Vautrin D. Food allergy to wheat flour in adults. [French] Allerg Immunol (Paris) 1999;31(1):22-5.
3. Varjonen E, Savolainen J, Mattila L, Kalimo K. IgE-binding components of wheat, rye, barley and oats recognized by immunoblotting analysis with sera from adult atopic dermatitis patients. Clin Exp Allergy 1994;24(5):481-9.
4. Baldo BA, Krilis S, Wrigley CW. Hypersensitivity to inhaled flour allergens. Comparison between cereals. Allergy 1980;35(1):45-56.
5. Varjonen E, Vainio E, Kalimo K. Life-threatening, recurrent anaphylaxis caused by allergy to gliadin and exercise. Clin Exp Allergy 1997;27(2):162-6.
Phil Lieberman, M.D.