Avoiding allergen triggers is one of the best ways to reduce your allergic symptoms. Avoidance is not always possible, but by finding out what you are reacting to, you’ll have more control over prevention. There are a range of tests that can be done to pinpoint your allergens. Rast allergy test is one method to find out.
RAST test (radioallergosorbent test) is done as a blood test for allergies to determine what substances a person is allergic to. It is ordered when a person has signs or symptoms that suggest an allergy to one or more substances including red itchy eyes, coughing, eczema, sneezing and what causes asthma.
A sample of your blood serum is exposed to a small disk to which the test allergen has been attached. If you are allergic, your IgE (immunoglobin E) antibodies will attach to the allergen in the disk. The RAST test is scored on a scale of 0 (absent or undetectable allergen specific IgE) to 6 (extremely high level of allergen specific IgE).
This is different from a skin prick allergy test, which determines allergy by the reaction of your skin to different substances. For example, if you exhibit a high level of IgE directed against pollen, the test may indicate you are allergic to pollen (or pollen-like) proteins. A person who has outgrown an allergy may still have a positive IgE years after exposure.
Advantages of an RAST test:
- Can be used on any age
- Can be used on people with extensive exzema or dermatitis
- It can be used at the same time as antihistamine treatment
Disadvantages of an RAST test:
- A positive response to an allergen indicates only a potential allergic reaction that may not be the cause of your symptoms
- It is much more expensive than a skin test
- The results are not immediately available
A RAST allergy test may assist as a basis to find out what triggers are present in some cases but seeing your health professional may be more satisfactory for others.