Wheat allergy is an allergy to wheat that typically presents as a food allergy, but can also be a contact allergy resulting from occupational exposure. The exact mechanism of this allergy is not yet clear. Wheat allergy may be immunoglobulin E-mediated or not,
Wheat allergy may be a misnomer. There are many allergenic components in wheat (for example: serine protease inhibitors, and ), with different responses attributed to different components. Twenty-seven potential wheat have been identified.
The allergy, or allergies, are often caused by reactions to the present in a wheat seed. While many reactions are caused by , allergenic components are also present in other biochemical forms. The most severe response is wheat-dependent exercise-induced anaphylaxis (WDEIA). WDEIA is attributed to an omega gliadin, which happens to be a relative of the protein that causes celiac disease.
Gluten sensitivity and Coeliac disease are two different diseases; however, the management is similar.[Costantino, A., Aversano, G., Lasagni, G., Smania, V., Doneda, L., Vecchi, M., ... & Elli, L. (2022). Diagnostic management of patients reporting symptoms after wheat ingestion. Frontiers in Nutrition, 9.] Management of wheat allergy consists of complete withdrawal of any food containing wheat or other gluten-containing cereals.
Types of allergies
Most wheat allergens are proteins,
including seed storage proteins, as noted above. There are four major classes of seed storage proteins:
,
, prolamins and glutenins.
Gluten allergy
The relevant
in wheat are
. Gliadins and
form the classic glutens—the causative agents of
celiac disease (CD). Distinct immune cells and antibody types differentiate gluten allergy from CD (see Comparative pathophysiology of gluten sensitivities).
Prolamin allergies
(gliadins) are associated with the more severe form of gluten allergy. Glutenin-induced allergies are often less severe. A proteomics-based study found a γ-gliadin isoform gene.
Glutelin allergies
Glutenin (wheat glutelin) is a predominant allergen in wheat.
Nine subunits of LMW-glutenin have been found to be in connection with wheat allergies.
Albumin and globulin allergy
At present, many of the allergens of wheat have not been characterized; however, the early studies found many to be in the albumin class.
A recent study in Europe confirmed the increased presence of allergies to amylase/trypsin inhibitors (
Serpin)
and lipid transfer protein (LPT),
but less reactivity to the globulin fraction.
The allergies tend to differ between populations (Italian, Japanese, Danish or Swiss), indicating a potential genetic component to these reactivities.
Other allergies
Wheat pollen and grass allergies
Respiratory allergies are an occupational disease that develops 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.
A later study showed that baker's allergy extends over a broad range of cereal grasses (wheat,
durum wheat,
triticale,
rye,
barley,
rye grass,
oats,
canary grass,
rice,
maize,
sorghum and
Johnson grass), though the greatest similarities were seen between wheat and rye,
and that these allergies show cross-reactivity between seed proteins and pollen proteins,
including a prominent
cross-reactivity between the common environment rye pollen and wheat gluten.
[.]
Derivative allergies
are made of a chain of dehydrated
Amino acid. When enzymes cut proteins into pieces, they add water back to the site at which they cut. This process is called enzymatic hydrolysis, or in the case of proteins it is called
proteolysis. The initial products of this
hydrolysis are polypeptides, and smaller products are called simply
Peptide; 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.
Signs and symptoms
Wheat allergies are not altogether different from other food allergies or respiratory allergies. However, two conditions, exercise/aspirin induced anaphylaxis and
urticaria, occur more frequently with wheat allergies.
Common symptoms of a wheat allergy include eczema (atopic dermatitis), urticaria, asthma, hay fever, angioedema (tissue swelling due to fluid leakage from blood vessels), abdominal cramps, nausea, and vomiting.
Reactions may become more severe with repeated exposure.
Asthma, anaphylaxis, nasal allergies
Exercise-induced anaphylaxis
Wheat
Gliadin 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.
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.
[ 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.][ 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.]
Baker's allergy
Baker's allergy has a ω-gliadin component and thioredoxin hB component.
Urticaria, atopy, eczema
Contact sensitivity,
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.
Rheumatoid arthritis
There appears to be an association of rheumatoid arthritis (RA) both with gluten sensitive enteropathy (GSE) and gluten allergies.
Neuropathies
Migraines. In the late 1970s it was reported that people with migraines had reactions to food allergens. Similarly to people with RA, the most common reaction among people with migraines 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 and hypertension declined.
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.
Diagnosis
Diagnoses of wheat allergy may deserve special consideration.[ Omega-5 gliadin, the most potent wheat allergen, cannot be detected in whole wheat preparations; it must be extracted and partially digested (similar to how it degrades in the intestine) to reach full activity.][
]
Prevention
Management of wheat allergy consists of complete withdrawal of any food containing wheat and other gluten-containing cereals (gluten-free diet).
In people with less severe forms of wheat-dependent exercise induced anaphylaxis (WDEIA), avoiding wheat consumption before exercise and other cofactors that trigger disease symptoms, such as nonsteroidal anti-inflammatory drugs and alcohol, can be sufficient to avoid an allergy.
Wheat is often a cryptic contaminant of many foods; more obvious items are bread crumbs, maltodextrin, bran, cereal extract, couscous, cracker meal, enriched flour, gluten, high-gluten flour, high-protein flour, seitan, semolina wheat, vital gluten, wheat bran, wheat germ, wheat gluten, wheat malt, wheat starch or whole wheat flour. Less obvious sources of wheat could be gelatinized starch, hydrolyzed vegetable protein, modified food starch, modified starch, natural flavoring, soy sauce, soybean paste, hoisin sauce, starch, natural gum, specifically beta-glucan, or vegetable starch.
Alternative cereals
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.
Treatment
Treatment for accidental ingestion of wheat products by allergic individuals varies depending on the sensitivity of the person. An antihistamine such as diphenhydramine may be prescribed. Sometimes prednisone will be prescribed to prevent a possible late phase Type I hypersensitivity reaction.
See also
-
Allergy (has diagrams showing involvement of different types of white blood cells)
-
Food allergy (has images of hives, skin prick test and patch test)
-
Gluten immunochemistry
-
List of allergens (food and non-food)
External links
