Beta-Lactoglobulin IgG Antibody, Qualitative (RAST)
A qualitative blood test for IgG antibodies to beta-lactoglobulin, a cow's-milk protein. Results require clinical context and do not alone diagnose milk allergy.
["A positive result shows IgG antibodies to beta-lactoglobulin but does not by itself confirm a milk allergy."]
Key facts at a glance
- LOINC
- 21109-4
- Short code
- Deprecated B-Lactoglob IgG RAST Ql
- Synonyms
- Deprecated B-Lactoglob IgG RAST Ql
- Category
- liver
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 10
- Ref high
- 40
- Critical range
- — – 500 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 84484
- SNOMED
- 302774002
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What is this test?
This test checks your blood for IgG antibodies directed against beta-lactoglobulin, a protein found in cow's milk. It reports whether such antibodies are detected rather than providing a specific concentration.
Why might I need this test?
A clinician may order this test when evaluating possible reactions to milk or milk-containing foods. It may also be used to assess immune exposure to beta-lactoglobulin.
How is the test performed?
A blood sample is analyzed using a RAST-type laboratory method, which determines whether IgG antibodies bind to beta-lactoglobulin. The result is reported as detected or not detected.
How do I prepare for the test?
No special preparation is usually required for this qualitative antibody test. Follow any instructions from your clinician, and tell the laboratory if you have recently eaten dairy products or started a new medication.
Reference range
Adult: 10-40 U/LN/A
No special preparation required. Avoid fatty meals before the test if possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Detected IgG antibodies may indicate previous exposure or an immune response to beta-lactoglobulin. However, food-specific IgG results are not a reliable stand-alone measure of clinical allergy and can occur in people without symptoms. A result should therefore be interpreted by your clinician alongside your symptoms, diet, and any other allergy testing.
Short name
Beta-lactoglobulin IgG antibody
Frequently asked questions
Does a positive result mean I am allergic to milk?
What is beta-lactoglobulin?
Is this the same as a milk-specific IgE test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy