FOOD ALLERGIES

FOOD ALLERGY

A food allergy is an adverse immune response to certain kinds of food. They are distinct from other adverse responses to food, such as food intolerance, pharmacological reactions, and toxin-mediated reactions. The protein in the food is the most common allergic component. These kinds of allergies occur when the body's immune system mistakenly identifies a protein as harmful. Some proteins or fragments of proteins are resistant to digestion and those that are not broken down in the digestive process are tagged by the Immunoglobin E (IgE). These tags fool the immune system into thinking that the protein is an invader. The immune system, thinking the organism (the individual) is under attack, sends white blood cells to attack, and that triggers an allergic reaction. These reactions can range from mild to severe. Allergic responses include dermatitis, gastrointestinal and respiratory distress, including such life-threatening anaphylactic responses as biphasic anaphylaxis and vasodilation; these require immediate emergency intervention. Individuals with protein allergies commonly avoid contact with the problematic protein. Some medications may prevent, minimize or treat protein allergy reactions. There is no cure. Treatment consists of either immunotherapy (desensitisation) or avoidance, in which the allergic person avoids all forms of contact with the food to which they are allergy. People diagnosed with a food allergy may carry an injectable form of epinephrine. Conditions caused by food allergies are classified into 3 groups according to the mechanism of the allergic response:

1.     Immunoglobin E-mediated (classic) – the most common type,( occurs shortly after eating and may involve anaphalaxis)

2.     Non-Immuniglonin E mediated – characterized by an immune response not involving immunoglobin E (may occur some hours after eating, complicating diagnosis).

3.     Immunoglobin E and/or non-Immunoglobin E-mediated – a hybrid of the above two types.

Signs and symptoms

Hives on the back are a common allergy symptom.

Classic immunoglobulin-E mediated food allergies are classified as type-I immediate Hypersensitivity reaction. These allergic reactions have an acute onset (from seconds to one hour) and may includes

·         Hives

·         Itching of mouth, lips, tongue, throat, eyes, skin, or other areas

·         Swelling (angioedema) of lips, tongue, eyelids, or the whole face

·         Difficulty swallowing

·         Runny or congested nose

·         Hoarse voice

·         Wheezing and/or shortness of breath

·         Nausea

·         Vomiting

·         Abdominal pain and/or stomach cramps

·         Lightheadedness

·         Fainting

·         death*

Symptoms of allergies vary from person to person. The amount of food needed to trigger a reaction also varies from person to person.
A severe case of an allergic reaction, caused by symptoms affecting the respiratory tract and blood circulation, is called anaphylaxis. When symptoms are related to a drop in blood pressure, the person is said to be in anaphylactic shock. Anaphylaxis occurs when Immunoglobin E are involved, and areas of the body that are not in direct contact with the food become affected and show symptoms. This occurs because no nutrients are circulated throughout the body, causing the widening of blood vessels. This vasodilation causes blood pressure to decrease, which leads to the loss of consciousness. Those with asthma or an allergy to peanuts, tree nuts, or seafood are at greater risk for anaphylaxis.

Common allergies

One of the most common food allergies is sensitivity to peanuts, a member of the bean family. Peanut allergies may be severe, but children with peanut allergies sometimes outgrow them. Tree nuts, including pecans, pine nuts, coconuts, and walnuts, are also common allergens. Individuals may be sensitive to one particular tree nut or to many different tree nuts. Also seeds that contains oils where protein is present, may elicit an allergic reaction.

Egg allergies affect about one in fifty children but are frequently outgrown by children when they reach age five. Typically the sensitivity is to proteins in the white, rather than the yolk.

Milk, from cows, goats or sheep, is another common food allergen, and many individuals are also unable to tolerate dairy products such as cheese. A small portion of children with a milk allergy, roughly ten percent, will have a reaction to beef. Beef contains a small amount of protein that is present in cow's milk^.

Other foods containing allergenic proteins include soy, wheat, fish, shellfish, fruits, vegetables, maize, spices, synthetic and natural colors, and chemical additives.

Although sensitivity levels vary by country, the most common food allergies are allergies to milk, eggs, peanuts, tree nuts, sea foods, shellfish, soy and wheat.

Diagnosis

There are four common types of allergy testing: skin prick test, patch test, blood test, and food challenges. These tests can be performed by the patient or an allergist and they can also go into further depth depending on the results.

Skin testing on the arm is a common way for detecting an allergy.

·         For skin prick test, a tiny board with protruding needles is used. The allergens are placed either on the board or directly on the skin. The board is then placed on the skin, in order to puncture the skin and for the allergens to enter the body. If a hive appears, the person will be considered positive for the allergy. This test only works for Immunoglobin E antibodies. Allergic reactions caused by other antibodies cannot be detected through skin prick tests.

Patch test

·         Patch testing is a method used to determine if a specific substance causes allergic inflammation of the skin. It tests for delayed food reactions

·         Blood testing is another useful diagnostic tool for evaluating Immunoglobin E-mediated food allergies. For example, the RAST (Radio Allergo Sorbent Test) detects the presence of Immunoglobin E antibodies to a particular allergen. It can show the amount of Immunoglobin E present to each allergy. Researchers have been able to determine "predictive values" for certain foods. These predictive values can be compared to the RAST blood test results. If a person’s RAST score is higher than the predictive value for that food, then there is over a 95% chance the person will have an allergic reaction (limited to rash and anaphylaxis reactions) if they ingest that food. Currently, predictive values are available for the following foods: milk, egg, peanut, fish, soy, and wheat. Blood tests allow for hundreds of allergens to be screened from a single sample, and cover food allergies as well as inhalants. However, non-Immunoglobin E mediated allergies cannot be detected by this method.

·         Food challenges test for allergens other than those caused by Immunoglobin E allergens. The allergen is given to the person in the form of a pill, so the person can ingest the allergen directly. The person is watched for signs and symptoms. The problem with food challenges is that they must be performed in the hospital under careful watch, due to the possibility of anaphylaxis. Food challenges, especially double-blind lacebo-controlled food challenges (DBPCFC), are the gold standard for diagnosis of food allergies, including most non-Immunoglobin E mediated reactions. Blind food challenges involve packaging the suspected allergen into a capsule, giving it to the patient, and observing the patient for signs or symptoms of an allergic reaction.

The best method for diagnosing food allergy is to be assessed by an allergist. The allergist will review the patient's history and the symptoms or reactions that have been noted after food ingestion. If the allergist feels the symptoms or reactions are consistent with food allergy, he/she will perform allergy tests.

In order to avoid an allergic reaction, a strict diet can be followed. It is difficult to determine the amount of allergenic food required to elicit a reaction, so complete avoidance should be attempted unless otherwise suggested by a qualified medical professional. In some cases, hypersensitive reactions can be triggered by exposures to allergens through skin contact, inhalation, kissing, participation in sports, blood transfusion, cosmetics, and alcohol.

REMEMBER TO ALWAYS STAY HEALTHY BECAUSE ADEQUATE NUTRITION, HEALTHIER SOCIETY.  FOR MORE INFO. CONTACT NUTRITIONIST KENNETH MERCY ON Kennethmercy@yahoo.com or call 08061344343.