on Monday, 23 January 2012. Posted in Diseases And Tests, Must Have Tests Written By: Archana Mahendra


RAST test is a blood test used for detecting allergies. Read on to know if you need one, how the test is done and what its results indicate.

The RAST test, also known as the Radioallergosorbent test or Allergy screen test is a blood test used to detect substances a person may be allergic to.

Scientifically called allergen-specific IgE ***antibody*** test, this test is used to determine the amount of immunoglobulin (IgE) antibodies in the blood.

IgE antibodies are actually proteins in the blood that tend to fasten to allergens (substances one may be allergic to). Hence, if one is allergic to dairy products, the IgE levels against dairy products will appear on the higher side in the test results.

RAST is ordered when:
This test is usually prescribed if one frequently experiences allergy symptoms like

RAST Trivia

Allergic diseases affect over 50 million Americans

Over 50% of homes have at least six detectable allergens present

Peanuts cause the most severe food-induced allergic reactions.

Boys appear to develop food allergies more than girls

  • coughing
  • runny or congested nose
  • sneezing
  • itch eyes
  • asthma
  • ***hives***
  • skin conditions like ***eczema*** or*** psoriasis***
  • upset stomach
  • nausea
  • This test may also be ordered at the end of an allergy treatment in order to monitor the effectiveness of ***immunotherapy*** or to check if one has outgrown an ***allergy***.

Test Procedure:
The test is a simple blood test, where a blood sample is drawn generally from the inside of the elbow or the back of the hand and sent to the lab for analysis. In the lab, the blood sample is exposed to allergens as recommended by your doctor. These could include allergens like dust mites, pollens, peanuts etc.

Reading the test results :
Test results can take a week or so to come. The RAST ratings are on a scale of 0 to 6, where 0 indicates nil or undetectable allergen specific IgE and 6 indicates extremely high levels of allergen specific IgE.

One must always let the doctor interpret the test results, as at times even if the IgE test result is negative, there could still be a small chance that a person does have an allergy; and at times even if the result is positive, the person may not actually have an allergic reaction when exposed to that allergen.

The doctors hence usually compare your RAST test report with your medical history and physical examination reports before arriving at any conclusion.

Depending on the test reports your doctor may treat you through allergy medications or immunotherapy and advice avoidance to your allergen or group of allergens.

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