Wheat allergy | |
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Wheat | |
Specialty | Immunology |
Wheat allergy is an allergy to wheat which typically presents itself as a food allergy, but can also be a contact allergy resulting from occupational exposure. Like all allergies, wheat allergy involves immunoglobulin E and mast cell response. [1] Typically the allergy is limited to the seed storage proteins of wheat. Some reactions are restricted to wheat proteins, while others can react across many varieties of seeds and other plant tissues. Wheat allergy is rare. Prevalence in adults was estimated to be 0.21% in a 2012 study in Japan. [2]
Wheat allergy may be a misnomer since there are many allergenic components in wheat, for example serine protease inhibitors, glutelins and prolamins and different responses are often attributed to different proteins. Twenty-seven potential wheat allergens have been successfully identified. [3] The most severe response is exercise/aspirin-induced anaphylaxis attributed to one omega gliadin that is a relative of the protein that causes celiac disease. [4] Other more common symptoms include nausea, urticaria, and atopy. [5]
Gluten sensitivity and Coeliac disease are two different diseases even if the management could be similar. [6] Management of wheat allergy consists of complete withdrawal of any food containing wheat or other gluten-containing cereals.
There are four major classes of seed storage proteins: albumins, globulins, prolamins and glutelins. Within wheat, prolamins are called gliadins and glutelins are called glutenins. These two protein groups form the classic glutens. While gluten is also the causative agent of celiac disease (CD), celiac disease can be contrasted to gluten allergy by the involvement of different immune cells and antibody types (See Comparative pathophysiology of gluten sensitivities), and because the list of allergens extend beyond the classic gluten category of proteins.[ citation needed ]
Prolamins and the closely related glutelins, a recent[ when? ] study in Japan found that glutenins are a more frequent allergen, however gliadins are associated with the most severe disease.[ citation needed ] A proteomics based study found a γ-gliadin isoform gene. [4]
Glutenin (wheat glutelin) is a predominant allergen in wheat. [4] Nine subunits of LMW-glutenin have been found to be in connection with wheat allergies.[ clarification needed ]
At present many of the allergens of wheat have not been characterized; however, the early studies found many to be in the albumin class. [7] A recent study in Europe confirmed the increased presence of allergies to amylase/trypsin inhibitors (serpins) [4] [8] and lipid transfer protein (LPT), [9] but less reactivity to the globulin fraction. [10] The allergies tend to differ between populations (Italian, Japanese, Danish or Swiss),[ citation needed ] 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. [11] 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, [12] and that these allergies show cross reactivity between seed proteins and pollen proteins, [13] including a prominent crossreactivity between the common environment rye pollen and wheat gluten. [14] [15]
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.[ citation needed ]
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. [16] These wheat polypeptides can cause immediate contact urticaria in susceptible people. [17]
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.[ citation needed ]
Common symptoms of a wheat allergy include eczema (atopic dermatitis), hives (urticaria), asthma, "hay fever" (allergic rhinitis), angioedema (tissue swelling due to fluid leakage from blood vessels), abdominal cramps, nausea, and vomiting. [18] Rarer symptoms include [ citation needed ] anaphylactic shock, anxiety, arthritis, bloated stomach, chest pains, depression or mood swings, diarrhea, dizziness, headache, joint and muscle aches and pains (may be associated with progressive arthritis), palpitations, psoriasis, irritable bowel syndrome (IBS), swollen throat or tongue, tiredness and lethargy, and unexplained cough.
Reactions may become more severe with repeated exposure.[ citation needed ]
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. [19] 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. [19] 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. [19] 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. [20]
Baker's allergy has a ω-gliadin component and thioredoxin hB component. [21] In addition, a gluten-extrinsic allergen has been identified as aspergillus amylase, added to flour to increase its baking properties.[ citation needed ]
Contact sensitivity, [22] atopic dermatitis, [23] 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. [24] As with exercise induced anaphylaxis, aspirin (also: tartrazine, sodium benzoate, sodium glutamate (MSG), sodium metabisulfite, tyramine) may be sensitizing factors for reactivity. [25] Studies of the wheat-dependent exercise induced anaphylaxis demonstrate that atopy and EIA can be triggered from the ingestion 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.[ citation needed ]
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.[ citation needed ]
There appears to be an association of rheumatoid arthritis (RA) both with gluten sensitive enteropathy (GSE) and gluten allergies. [26] 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. [27] 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.[ spelling? ] [28]
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. [29] Some specific instances are attributed to wheat. [30]
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. [31]
This section needs additional citations for verification .(May 2021) |
Diagnoses of wheat allergy may deserve special consideration. [19] 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. Other studies show that digestion of wheat proteins to about 10 amino acids can increase the allergic response 10 fold. Certain allergy tests may not be suitable to detect all wheat allergies, resulting in cryptic allergies. Because many of the symptoms associated with wheat allergies, such as eczema and asthma, may be related or unrelated to a wheat allergy, medical deduction can be an effective way of determining the cause. If symptoms are alleviated by immunosuppressant drugs, such as prednisone, an allergy-related cause is likely. If multiple symptoms associated with wheat allergies are present in the absence of immunosuppressants then a wheat allergy is probable. [19]
Management of wheat allergy consists of complete withdrawal of any food containing wheat and other gluten-containing cereals (gluten-free diet). [32] [33] However, some patients can tolerate barley, rye or oats. [34]
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 enough to avoid an allergy. [33]
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, soy bean paste, hoisin sauce, starch, vegetable gum, specifically beta-glucan, vegetable starch.[ citation needed ]
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 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. [35] Severe allergic reactions (anaphalaxis) may require treatment with an epinephrine pen, which is an injection device designed to be used by a non-healthcare professional when emergency treatment is warranted. [36]
Gluten is a structural protein naturally found in certain cereal grains. The term gluten usually refers to the elastic network of a wheat grain's proteins, gliadin and glutenin primarily, that forms readily with the addition of water and often kneading in the case of bread dough. The types of grains that contain gluten include all species of wheat, and barley, rye, and some cultivars of oat; moreover, cross hybrids of any of these cereal grains also contain gluten, e.g. triticale. Gluten makes up 75–85% of the total protein in bread wheat.
A gluten-free diet (GFD) is a nutritional plan that strictly excludes gluten, which is a mixture of prolamin proteins found in wheat, as well as barley, rye, and oats. The inclusion of oats in a gluten-free diet remains controversial, and may depend on the oat cultivar and the frequent cross-contamination with other gluten-containing cereals.
Food intolerance is a detrimental reaction, often delayed, to a food, beverage, food additive, or compound found in foods that produces symptoms in one or more body organs and systems, but generally refers to reactions other than food allergy. Food hypersensitivity is used to refer broadly to both food intolerances and food allergies.
Gliadin is a class of proteins present in wheat and several other cereals within the grass genus Triticum. Gliadins, which are a component of gluten, are essential for giving bread the ability to rise properly during baking. Gliadins and glutenins are the two main components of the gluten fraction of the wheat seed. This gluten is found in products such as wheat flour. Gluten is split about evenly between the gliadins and glutenins, although there are variations found in different sources.
Peanut allergy is a type of food allergy to peanuts. It is different from tree nut allergies, because peanuts are legumes and not true nuts. Physical symptoms of allergic reaction can include itchiness, hives, swelling, eczema, sneezing, asthma attack, abdominal pain, drop in blood pressure, diarrhea, and cardiac arrest. Anaphylaxis may occur. Those with a history of asthma are more likely to be severely affected.
Soy allergy is a type of food allergy. It is a hypersensitivity to ingesting compounds in soy, causing an overreaction of the immune system, typically with physical symptoms, such as gastrointestinal discomfort, respiratory distress, or a skin reaction. Soy is among the eight most common foods inducing allergic reactions in children and adults. It has a prevalence of about 0.3% in the general population.
Egg allergy is an immune hypersensitivity to proteins found in chicken eggs, and possibly goose, duck, or turkey eggs. Symptoms can be either rapid or gradual in onset. The latter can take hours to days to appear. The former may include anaphylaxis, a potentially life-threatening condition which requires treatment with epinephrine. Other presentations may include atopic dermatitis or inflammation of the esophagus.
A tree nut allergy is a hypersensitivity to dietary substances from tree nuts and edible tree seeds causing an overreaction of the immune system which may lead to severe physical symptoms. Tree nuts include almonds, Brazil nuts, cashews, chestnuts, filberts/hazelnuts, macadamia nuts, pecans, pistachios, shea nuts and walnuts.
Triticeae is a botanical tribe within the subfamily Pooideae of grasses that includes genera with many domesticated species. Major crop genera found in this tribe include wheat, barley, and rye; crops in other genera include some for human consumption, and others used for animal feed or rangeland protection. Among the world's cultivated species, this tribe has some of the most complex genetic histories. An example is bread wheat, which contains the genomes of three species with only one being a wheat Triticum species. Seed storage proteins in the Triticeae are implicated in various food allergies and intolerances.
Gluten is the seed storage protein in mature wheat seeds. It is the sticky substance in bread wheat which allows dough to rise and retain its shape during baking. The same, or very similar, proteins are also found in related grasses within the tribe Triticeae. Seed glutens of some non-Triticeae plants have similar properties, but none can perform on a par with those of the Triticeae taxa, particularly the Triticum species. What distinguishes bread wheat from these other grass seeds is the quantity of these proteins and the level of subcomponents, with bread wheat having the highest protein content and a complex mixture of proteins derived from three grass species.
Gluten-related disorders is the term for the diseases triggered by gluten, including celiac disease (CD), non-celiac gluten sensitivity (NCGS), gluten ataxia, dermatitis herpetiformis (DH) and wheat allergy. The umbrella category has also been referred to as gluten intolerance, though a multi-disciplinary physician-led study, based in part on the 2011 International Coeliac Disease Symposium, concluded that the use of this term should be avoided due to a lack of specificity.
Anti-gliadin antibodies are produced in response to gliadin, a prolamin found in wheat. In bread wheat it is encoded by three different alleles, AA, BB, and DD. These alleles can produce slightly different gliadins, which can cause the body to produce different antibodies. Some of these antibodies can detect proteins in specific grass taxa such as Triticeae, while others react sporadically with certain species in those taxa, or over many taxonomically defined grass tribes.
Glutelins are a class of prolamin proteins found in the endosperm of certain seeds of the grass family. They constitute a major component of the protein composite collectively referred to as gluten. Glutenin is the most common glutelin, as it is found in wheat and is responsible for some of the refined baking properties in bread wheat. The glutelins of barley and rye have also been identified. Glutelins are the primary protein form of energy storage in the endosperm of rice grains.
Oat sensitivity represents a sensitivity to the proteins found in oats, Avena sativa. Sensitivity to oats can manifest as a result of allergy to oat seed storage proteins either inhaled or ingested. A more complex condition affects individuals who have gluten-sensitive enteropathy in which there is an autoimmune response to avenin, the glutinous protein in oats similar to the gluten within wheat. Sensitivity to oat foods can also result from their frequent contamination by wheat, barley, or rye particles.
The immunochemistry of Triticeae glutens is important in several inflammatory diseases. It can be subdivided into innate responses, class II mediated presentation, class I mediated stimulation of killer cells, and antibody recognition. The responses to gluten proteins and polypeptide regions differs according to the type of gluten sensitivity. The response is also dependent on the genetic makeup of the human leukocyte antigen genes. In gluten sensitive enteropathy, there are four types of recognition, innate immunity, HLA-DQ, and antibody recognition of gliadin and transglutaminase. With idiopathic gluten sensitivity only antibody recognition to gliadin has been resolved. In wheat allergy, the response pathways are mediated through IgE against other wheat proteins and other forms of gliadin.
Non-celiac gluten sensitivity (NCGS) or gluten sensitivity is a controversial disorder which can cause both gastrointestinal and other problems.
Exercise-induced anaphylaxis is a rare condition in which anaphylaxis, a serious or life-threatening allergic response, is brought on by physical activity. Approximately 5–15% of all reported cases of anaphylaxis are thought to be exercise-induced.
Fish allergy is an immune hypersensitivity to proteins found in fish. Symptoms can be either rapid or gradual in onset. The latter can take hours to days to appear. The former may include anaphylaxis, a potentially life-threatening condition which requires treatment with epinephrine. Other presentations may include atopic dermatitis or inflammation of the esophagus. Fish is one of the eight common food allergens which are responsible for 90% of allergic reactions to foods: cow's milk, eggs, wheat, shellfish, peanuts, tree nuts, fish, and soy beans.
Shellfish allergy is among the most common food allergies. "Shellfish" is a colloquial and fisheries term for aquatic invertebrates used as food, including various species of molluscs such as clams, mussels, oysters and scallops, crustaceans such as shrimp, lobsters and crabs, and cephalopods such as squid and octopus. Shellfish allergy is an immune hypersensitivity to proteins found in shellfish. Symptoms can be either rapid or gradual in onset. The latter can take hours to days to appear. The former may include anaphylaxis, a potentially life-threatening condition which requires treatment with epinephrine. Other presentations may include atopic dermatitis or inflammation of the esophagus. Shellfish is one of the eight common food allergens, responsible for 90% of allergic reactions to foods: cow's milk, eggs, wheat, shellfish, peanuts, tree nuts, fish, and soy beans.
A food allergy to sesame seeds has prevalence estimates in the range of 0.1–0.2% of the general population, and are higher in the Middle East and other countries where sesame seeds are used in traditional foods. Reporting of sesame seed allergy has increased in the 21st century, either due to a true increase from exposure to more sesame foods or due to an increase in awareness. Increasing sesame allergy rates have induced more countries to regulate food labels to identify sesame ingredients in products and the potential for allergy. In the United States, sesame became the ninth food allergen with mandatory labeling, effective 1 January 2023.
For both wheat allergy and coeliac disease the dietary avoidance of wheat and other gluten-containing cereals is the only effective treatment.
Wheat-dependent exercise-induced anaphylaxis (WDEIA) is a rare, but potentially severe food allergy exclusively occurring when wheat ingestion is accompanied by augmenting cofactors. (...) The most reliable prophylaxis of WDEIA is a gluten-free diet. In less severe cases, a strict limitation of wheat ingestion before exercise and avoidance of other cofactors may be sufficient.