lunes, 1 de abril de 2019

Wheat Allergy

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By Sally Robertson, B.Sc.Reviewed by Tomislav Meštrović, MD, PhD

Wheat allergy, a condition that affects millions of people, occurs when the immune system becomes sensitized to wheat and then overreacts when foods such as cereal, bread, pasta or pizza are eaten. Wheat is also found in drinks such as beer, which can also trigger an allergic reaction.

Gluten-free bread. Image Copyright: ChameleonsEye / Shutterstock

This type of allergy usually affects younger children, with around 65% growing out of it by the age of 12. Generally, people are at a greater risk of developing a wheat allergy if they have a family history of allergies such as asthma or eczema.

Wheat allergy is characterized by the activation of T helper type 2 (Th2) cells which are necessary for humoral immunity and play a pivotal role in coordinating the immune response. Such activation results in immunoglobulin E and non-immunoglobulin E mediated reactions (the latter representing much less understood pathophysiological mechanism).

Symptoms

A person with a wheat allergy is likely to experience symptoms of allergic reaction within minutes to hours after exposure to wheat. The symptoms that arise are usually mild, but people can also develop a severe and life threatening reaction called anaphylaxis. Accurate diagnosis and correct management of wheat allergy is therefore essential.

As is the case with other food allergies, the symptoms that may arise with a wheat allergy include the following:

Nausea and vomiting
Abdominal pain, diarrhea and indigestion
Asthma
Runny or congested nose
Sneezing
Headache
Anaphylaxis

If a person develops any of these symptoms after exposure to wheat, they should consult an allergist or an immunologist.

Diagnosis

If a doctor suspects a person has a wheat allergy, they will ask about the person’s medical history and any family history of allergies. A skin-prick test and/or blood test may be arranged. For the skin-prick test, a small amount of wheat protein is placed on the skin of the back or arm, which is then pricked with a small probe to let the protein underneath the skin. If a small bump or hive then develops at this site, the person may have an allergy.

For the blood test, a sample is checked for the presence of immunoglobulin (IgE) antibodies to wheat proteins. Nevertheless, the presence of specific serum IgE antibodies to wheat without a history of symptoms after wheat exposure is not considered to be diagnostic as many people can be sensitive to wheat, but can tolerate wheat exposure (most notably in grass pollen sensitive individuals).

As certain symptoms can overlap (most notably from the gastrointestinal corner), a wheat allergy should be differentiated from “gluten intolerance” or celiac disease where the underlying pathophysiological mechanism is an abnormal immune reaction to gluten.

Management

If a wheat allergy is diagnosed, foods that contain wheat such as bread and pasta should be avoided, as well as non-food products with ingredients containing wheat such as cosmetics. Foods that are not intended to contain wheat may become contaminated with it during manufacture or preparation and people with an allergy should also avoid any items that display a warning that the product was made or packaged in a place where wheat is also processed.

If exposure does accidentally occur, symptoms may be controlled with antihistamines or corticosteroids. Epinephrine is the only drug that can reverse anaphylaxis, which can arise within just seconds of exposure to wheat. When this occurs, the body releases a mass of chemicals that can cause constriction of the airways, a sharp fall in blood pressure and shock.

If a person is at risk of having a severe reaction, they will be prescribed an auto-injector and taught how to self-administer epinephrine. People should always ensure they have two doses available, since the reaction may recur. The medication should be taken as soon as a person suspects they have eaten a food containing wheat or if they start to experience symptoms of an allergic reaction such as a tight throat or trouble breathing.