What is a Radioallergosorbent Test (RAST)?

Most Americans suffer from allergies. In addition to food allergies, the most common are triggered by exposure to dust particles, trees, molds and grasses.

When your body is exposed to an allergy trigger (also known as an allergen), specific antibodies are secreted to fight them off, producing the unpleasant symptoms associated with an allergy such as sneezing and violent coughing.

If you suspect that you have an allergy to a particular object, your doctor may recommend a blood or skin test to identify the allergen. An elimination diet may be recommended.

Patients with a history of allergies to certain foods can also be subjected to blood tests to determine which foods may be the culprits. One popular form of an allergy blood test is the radioallergosorbent test.

What is a Radioallergosorbent Test?

A radioallergosorbent test (RAST) is a blood test whose purpose is to evaluate how your immune system responds to specific foreign elements or allergens. It measures the allergy-triggering antibodies in your blood, known as immunoglobulin E (IgE) antibodies.

Your doctor may recommend other tests if he/she suspects that your condition is triggered by something else rather than an allergy, states Food Allergy Research & Education, Inc.

Necessity of Allergy Blood Tests

The doctor handling your case may propose a blood test under such scenarios;

1. If your body cannot withstand the several needle scratches necessary for skin testing;
2. If you suffer from a heart condition;
3. If the medications you're using tend to obstruct the test results and you cannot discontinue taking them anytime soon. Examples of such medicines include steroids and antihistamines;
4. If you have past history of suffering from a critical allergic reaction known as anaphylaxis;
5. If you’re likely to have an intense reaction during skin testing;
6. If you have dermatitis, eczema, psoriasis or any other critical skin condition;
7. If you have a poorly-managed asthma complications.

Your doctor may also prefer a radioallergosorbent test in order to determine whether you’re overcoming the allergy by responding to the allergy treatments (immunotherapy). When your blood test reads positive, it indicates that some allergen-specific antibodies were traced in your blood and hence you have an allergy.

Advantages and Disadvantages of RAST

One of the major advantages of Radioallergosorbent test is that it can be done at any time without any consideration to the medications you’re prescribed to take. Moreover, unlike skin testing, this test requires only one needle stick. This makes it favorable for people who are scared of needles such as infants and very young kids.

However, the test may be less sensitive and more expensive than skin tests. Furthermore, it takes longer to get the results since the blood sample has to be sent to a laboratory for assessment.

Side Effects of Radioallergosorbent Test

Radioallergosorbent test is relatively safe and has minor side effects such as bleeding, redness and swelling at the spot where the needle was injected.