Gluten
Summary
Wheat is the most widely consumed food grain in the world. The wheat kernel contains approximately 8-15% protein content of which 85%–90% is gluten. Gluten is made up of insoluble gliadins as well as high and low molecular weight glutenins, which are responsible for IgE-mediated reactions in wheat allergy, affecting an estimated 0.4% of the world’s population. Symptoms of wheat allergy usually develop within minutes to hours after ingestion and affect the GI tract (vomiting, colic, diarrhea), skin (urticaria, eczema), respiratory tract (upper respiratory, asthma), or include systemic anaphylactic reactions. Symptoms can also manifest as baker’s asthma (from inhaled flour), atopic dermatitis (from skin exposure), urticaria (forming hives after skin exposure), or wheat-dependent exercise-induced anaphylaxis).
Epidemiology
Worldwide distribution
An estimated 0.4% of the world’s population are allergic to wheat proteins, where the majority of cases are children, where most (45-69%) become tolerant to wheat by age 6. Omega-5 gliadin is implicated in severe immediate-type reactions in children and wheat-dependent, exercise-induced anaphylaxis. The prevalence of wheat allergy does vary according to age and location. It has been cited as the third most common allergen in Germany, Japan, Finland, and in preschool children in the USA. In Europe overall, the prevalence is estimated to be less than 1 %.
Pediatric issues
In children with wheat allergy, atopic disorders often coexist with atopic dermatitis (53–87%), asthma (48–75%), and allergic rhinitis (34–62%) is often present. About 90% of infants are also allergic to other foods, most commonly cow’s milk and/or egg, and less frequently fish, soya, and nuts. Grass sensitization is associated with an increased risk for wheat sensitization over time. In children with specific IgE to Phl p12 (profilin) and to MUXF3 CCD (Cross-reactive Carbohydrate Determinant), cross-reactivity to grass–wheat appears to be more common. Additional studies have hypothesized a number of possible environmental factors that may affect the risk of developing wheat allergy, such as delaying exposure to wheat and breastfeeding, with inconclusive results.
Route Of Exposure
Main
Ingestion.
Secondary
Inhalation and skin exposure.
Clinical Relevance
Gluten-related disorders typically include wheat allergy, celiac disease and the suggested condition of non-celiac gluten sensitivity.
Wheat allergy is an IgE-mediated reaction to the insoluble gliadins that make up gluten in wheat. Wheat allergic subjects can also be sensitized to high and low molecular weight glutenins.
The symptoms usually develop within minutes to hours after ingestion and usually affect the GI tract (vomiting, colic, diarrhea), skin (urticaria, eczema), respiratory tract (upper respiratory, asthma), or multiple systems (anaphylaxis). Symptoms can also manifest as Baker’s asthma and rhinitis (from inhaled flour), atopic dermatitis (from skin exposure), urticaria (forming hives after skin exposure), or wheat-dependent exercise-induced anaphylaxis (when wheat is consumed before vigorous physical activity).
Prevention And Therapy
Allergen immunotherapy
The efficacy and safety of vital wheat gluten (gluten separated from wheat) oral immunotherapy was assessed in a randomized controlled trial in 46 patients with wheat allergy aged 4.2–22.3 years. Both low and high-dose immunotherapy induced desensitization in about 50 % of the subjects after 1 year of treatment. After two years, low-dose immunotherapy resulted in 30 % desensitization, and 13 % of patients had sustained unresponsiveness. Among 7822 treatments with low-dose immunotherapy in the first year, 15.4 % were associated with adverse reactions, of which 0.04% were classed as severe. Amongst 7921 placebo doses, 5.8 % were associated with adverse reactions with no severe reactions.
Prevention strategies
Avoidance
The mainstay of management for wheat allergy is dietary avoidance.
Other topics
In general, wheat allergic patients are able to tolerate other cereal grains. To treat reactions from accidental exposure, an epinephrine auto-injector can be prescribed for patients who have a history of systemic reactions. For wheat-dependent exercise-induced anaphylaxis, ancestral wheat (which does not contain omega-5 gliadin) may be useful. For occupational exposure, measures need to be put in place to minimize inhalation exposure.
Cross-Reactivity
At the time of writing, there is limited information on gluten (either gliadin or glutenin) cross-reactivity.
References
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- Ricci G, Andreozzi L, Cipriani F, Giannetti A, Gallucci M, Caffarelli C. Wheat Allergy in Children: A Comprehensive Update. Medicina (Kaunas). 2019;55(7).
- Burkhardt JG, Chapa-Rodriguez A, Bahna SL. Gluten sensitivities and the allergist: Threshing the grain from the husks. Allergy. 2018;73(7):1359-68.
- ITIS. Triticum L. 2021 [cited 2021 13.12.21]. Available from: https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=42236#null.
- Kucek LK, Veenstra LD, Amnuaycheewa P, Sorrells ME. A Grounded Guide to Gluten: How Modern Genotypes and Processing Impact Wheat Sensitivity. Comprehensive Reviews in Food Science and Food Safety. 2015;14(3):285-302.
- Nowak-Węgrzyn A, Wood RA, Nadeau KC, Pongracic JA, Henning AK, Lindblad RW, et al. Multicenter, randomized, double-blind, placebo-controlled clinical trial of vital wheat gluten oral immunotherapy. J Allergy Clin Immunol. 2019;143(2):651-61.e9.
- Allergome.org. Gluten 2021 [cited 2021 13.12.21]. Available from: http://www.allergome.org/script/search_step2.php.