The primary blood test associated with itchy skin is the RAST (Radioallergosorbent test).
Understanding the RAST Test
The RAST test is a blood test that helps identify specific allergies that could be causing itchy skin. Here's how it works:
- IgE Antibodies: The test measures the amount of specific IgE antibodies in your blood. These antibodies are produced by your immune system when it overreacts to harmless substances, known as allergens.
- Allergic Reaction: If you have elevated levels of specific IgE antibodies, it indicates a potential allergic reaction to that particular allergen. This reaction can manifest as itchy skin, among other symptoms.
- Procedure: A blood sample is taken and sent to a lab, where it is analyzed for the presence of IgE antibodies to various allergens.
- Interpretation: High levels of specific IgE antibodies to an allergen suggest you may have an allergy to it.
Why is a Blood Test Needed for Itchy Skin?
While skin prick tests are another common method to check allergies, sometimes a blood test like the RAST is preferred or necessary:
- Skin Conditions: When the skin is severely inflamed or has eczema, a skin prick test might not be suitable.
- Medications: Certain medications, like antihistamines, can interfere with skin prick test results.
- Convenience: Blood tests can be more convenient for those who are anxious about skin tests or have difficulty staying still for the skin test procedure.
- Comprehensive Allergy Screening: The RAST test can be useful to screen for a broad panel of allergens.
Differences Between RAST and Skin Prick Tests
| Feature | RAST Test | Skin Prick Test |
|---|---|---|
| Type | Blood test | Skin test |
| Method | Measures IgE antibodies in blood | Involves pricking skin with allergens |
| Interference | Not affected by antihistamines | Can be affected by antihistamines |
| Suitability | Suitable with severe skin conditions | Less suitable with severe skin conditions |
| Convenience | More convenient for some patients | Requires patient to stay still for a certain time |
Conclusion
If you are experiencing itchy skin, it's important to consult with your doctor to determine the cause. The RAST test can be a valuable tool in diagnosing allergies as a potential culprit.
