Wheat allergy

Prolamins and the closely related glutelins, a recent study in Japan found that glutenins are a more frequent allergen, however gliadins are associated with the most severe disease. A proteomics based study found a γ-gliadin isoform gene.[3]

Glutenin (wheat glutelin) is a predominant allergen in wheat.[3] Nine subunits of LMW-glutenin have been linked in connection with wheat allergies.

At present many of the allergens of wheat have not been characterized; however, the early studies found many to be in the albumin class.[5] A recent study in Europe confirmed the increased presence of allergies to amylase/trypsin inhibitors (serpins)[3][6] and lipid transfer protein (LPT),[7] but less reactivity to the globulin fraction.[8] The allergies tend to differ between populations (Italian, Japanese, Danish or Swiss), indicating a potential genetic component to these reactivities.

Respiratory allergies are an occupational disease that develop in food service workers. Previous studies detected 40 allergens from wheat; some cross-reacted with rye proteins and a few cross-reacted with grass pollens.[9] A later study showed that baker's allergy extend over a broad range of cereal grasses (wheat, durum wheat, triticale, cereal rye, barley, rye grass, oats, canary grass, rice, maize, sorghum and Johnson grass) though the greatest similarities were seen between wheat and rye,[10] and that these allergies show cross reactivity between seed proteins and pollen proteins,[11] including a prominent crossreactivity between the common environment rye pollen and wheat gluten.[12][13]

Proteins are made of a chain of dehydrated amino acids. When enzymes cut proteins into pieces they add water back to the site at which they cut, called enzymatic hydrolysis, for proteins it is called proteolysis. The initial products of this hydrolysis are polypeptides, and smaller products are called simply peptides; these are called wheat protein hydrolysates. These hydrolysates can create allergens out of wheat proteins that previously did not exist by the exposure of buried antigenic sites in the proteins.

When proteins are cut into polypeptides, buried regions are exposed to the surface, and these buried regions may possibly be antigenic. Such hydrolyzed wheat protein is used as an additive in foods and cosmetics. The peptides are often 1 kD in size (9 amino acid residues in length) and may increase the allergic response.[14] These wheat polypeptides can cause immediate contact urticaria in susceptible people.[15]

Wheat gliadins and potentially oat avenins are associated with another disease, known as wheat-dependent exercise induced anaphylaxis (WDEIA) which is similar to baker's allergy as both are mediated by IgE responses.[17] In WDEIA, however, the ω-gliadins or a high molecular weight glutenin subunit, and similar proteins in other Triticeae genera, enter the blood stream during exercise where they cause acute asthmatic or allergic reaction.[17] Wheat may specifically induce WDEIA and certain chronic urticaria because the anti-gliadin IgE detects ω₅-gliadins expressed by most of the Gli-B1 alleles, but prolamins extracted from rye or wheat/rye translocates invoke almost no responses.[17] The Gli-B1 gene in wheat, Triticum aestivum, comes from the progenitor species Aegilops speltoides. This indicates that nascent mutations on the B genome of wheat are from a small number of cultivated Triticeae species.[18]

Baker's allergy has a ω-gliadin component and thioredoxin hB component.[19] In addition, a gluten-extrinsic allergen has been identified as aspergillus amylase, added to flour to increase its baking properties.

Allergic urticaria on the shin

Contact sensitivity,[20] atopic dermatitis,[21] eczema, and urticaria appear to be related phenomena, the cause of which is generally believed to be the hydrophobic prolamin components of certain Triticeae, Aveneae cultivars. In wheat one of these proteins is ω-gliadin (Gli-B1 gene product). A study of mothers and infants on an allergen-free diet demonstrated that these conditions can be avoided if wheat sensitive cohort in the population avoid wheat in the first year of life.[22] As with exercise induced anaphylaxis, aspirin (also: tartrazine, sodium benzoate, sodium glutamate (MSG), sodium metabisulfite, tyramine) may be sensitizing factors for reactivity.[23] Studies of the wheat-dependent exercise induced anaphylaxis demonstrate that atopy and EIA can be triggered from the ingestion of that aspirin and probably NSAIDs allow the entry of wheat proteins into the blood, where IgE reacts within allergens in the dermal tissues. Some individuals may be so sensitive that low dose aspirin therapy can increase risk for both atopy and WDEIA.

Wheat allergies were also common with contact dermatitis. A primary cause was the donning agent used for latex gloves prior to the 1990s, however most gloves now use protein free starch as a donning agent.

There appears to be an association of rheumatoid arthritis (RA) both with gluten sensitive enteropathy (GSE) and gluten allergies.[24] RA in GSE/CD may be secondary to tissue transglutaminase (tTG) autoimmunity. In a recent study in Turkey, 8 of 20 RA patients had wheat reactivities on the radioallergosorbent test (RAST). When this allergic food and all other patient specific RAST+ foods were removed half of the patients had improved RA by serological markers. In patients with wheat allergies, rye was effectively substituted.[25] This may indicate that some proportion of RA in GSE/CD is due to downstream effects of allergic responses. In addition, cross-reactive anti-beef-collagen antibodies (IgG) may explain some rheumatoid arthritis (RA) incidences.[26]

Migraines. In the late 1970s it was reported that people with migraines had reactions to food allergens, like RA, the most common reaction was to wheat (78%), orange, eggs, tea, coffee, chocolate, milk, beef, corn, cane sugar, and yeast. When 10 foods causing the most reactions were removed migraines fell precipitously, hypertension declined.[27] Some specific instances are attributed to wheat.[28]

Autism. Parents of children with autism often ascribe the children's gastrointestinal symptoms to allergies to wheat and other foods. The published data on this approach are sparse, with the only double-blind study reporting negative results.[29]

Triticeae gluten-free oats (free of wheat, rye or barley) may be a useful source of cereal fiber. Some wheat allergies allow the use of rye bread as a substitute. Rice flour is a commonly used alternative for those allergic to wheat. Wheat-free millet flour, buckwheat, flax seed meal, corn meal, quinoa flour, chia seed flour, tapioca starch or flour, and others can be used as substitutes.