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What is an Allergy Test?

An allergy test is used to identify substances that can cause allergic reactions in an individual. An allergy is a hypersensitive immune reaction to an external agent (allergen) that is recognised as harmful to the body.

In response to the presence of an allergen, the body overreacts by producing antibodies called immunoglobulin E (IgE), thereby releasing chemicals to elicit an allergic reaction. These reactions can range from mild, such as sneezing, to life-threatening conditions such as anaphylaxis. An allergy test is hence needed to determine which the allergens a person hyper reacts to. 

Children are more susceptible to food allergies than adults, and they usually outgrow them with age. Most allergies are caused by foods, such as milk, eggs, soy, wheat, nuts, fish, shellfish and pollen. Food sensitivity is different from an allergy in that it is only an intolerance to a particular food item, such as lactose, gluten and monosodium glutamate. It indicates that the body cannot digest certain food items and hence the symptoms of food allergy are limited to nausea, vomiting, flatulence and diarrhoea.

Gluten sensitivity is different from celiac disease; the former is an intolerance to gluten while the latter is an autoimmune condition. in which. the immune system damages intestine on consuming gluten. Wheat allergy is an entirely different condition and has more severe symptoms than gluten intolerance.

  1. Why is an Allergy test performed?
  2. How do you prepare for an Allergy test?
  3. How is an Allergy test performed?
  4. What do Allergy test results indicate?

An allergy test is indicated when the patient exhibits any one of the following symptoms:

There are no special preparations required for this test. If you are taking any medications or drugs, it is advised to inform the physician prior to the test.

A physician or allergist will first take a complete medical history followed by a thorough physical examination. Allergy test is then conducted in the following ways:

  • Oral test: An allergist will give small amounts of the suspected food allergens in the form of a capsule or injection. The patient will be closely monitored to observe for a reaction. If the reaction is positive, it is quickly responded with treatment.
  • Elimination diet: This method is used to find out specific foods which may be causing allergy. The person is asked to eliminate suspected food items immediately from their diet. Then, each food item is included one by one, observing for an allergic reaction. This method is not recommended for persons with a risk of a severe reaction.
  • Skin prick test: In this test, an allergist will prick a small amount of the suspected item into the skin of the forearm or on the back. If a red, itchy bump develops at the injection site, it signifies allergy to that particular food item.
  • Blood test: This test checks for the number of  IgE antibodies in blood. A blood sample will be drawn from the arm for testing. There may be a slight stinging sensation at the time of the prick. This test usually lasts for 5-10 minutes.

Normal results: If there is no reaction to a substance taken orally or injected, it means the person is not allergic to that substance.

Abnormal results: If there is a reaction to the substance injected or ingested, it signifies an allergy to that substance.

The best way to take care of allergies is to avoid the substance that causes the allergy and eliminate it from the diet completely if it is a food item. Labels on food items should be carefully read as they may contain allergy-causing substances. Family members, caretakers, teachers, restaurants and people preparing and serving foods should be warned to not include such food items while cooking meals. If a person is at a high risk of developing an allergic reaction, an allergist will provide an epinephrine injection to be taken during an acute episode.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. This information is purely from an educational perspective and is in no way a substitute for medical advice from a qualified doctor.

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References

  1. American Academy of Allergy, Asthma and Immunology [Internet]. Milwaukee (WI); ALLERGY TESTING
  2. Asthma and Allergy Foundation of America [Internet]. Landover (MD): Asthma and Allergy Foundation of America; Food Allergies
  3. Johns Hopkins Medicine [Internet]. The Johns Hopkins University, The Johns Hopkins Hospital, and Johns Hopkins Health System; Food Allergies
  4. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; Allergy Tests: Test Overview
  5. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; Diagnostic Tests for Allergies
  6. Kurowski K, Boxer RW. Food Allergies: Detection and Management. American Family Physician [Internet]