Understanding Your Medical Test: What It Is, How It Is Performed, and How to Prepare
This blood test measures whether your immune system reacts to Baker's yeast by releasing histamine, helping diagnose yeast allergies.
{"A blood test that checks for allergic reaction to Baker's yeast","Measures histamine released by immune cells when exposed to yeast proteins","Used to diagnose yeast allergies or sensitivities","Requires a simple blood draw","Results help guide dietary and treatment decisions"}
Key facts at a glance
- LOINC
- 7784-2
- Short code
- BYHR
- Synonyms
- Baker's yeast BasoBnd Ab Qn
- Category
- chemistry
- Sample
- whole-blood
- Container
- Heparinized (sodium heparin or lithium heparin) blood collection tube; EDTA tubes may be used for some assay platforms but heparin is preferred to preserve basophil function.
- Units
- N/A
- Ref low
- 10
- Ref high
- 40
- Critical range
- — – 500 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 1 years
- Method
- Basophil activation test or whole-blood histamine release assay using baker's yeast (Saccharomyces cerevisiae) as a stimulating allergen. Histamine release is measured by enzyme immunoassay or fluorometric assay following incubation of whole blood with baker's yeast extract.
- CPT
- 86003
- SNOMED
- 39579001
- Specimen volume
- 5-10 mL of whole blood; minimum 3 mL for pediatric samples.
- Stability
- Specimen should be processed within 2-4 hours of collection. Do not refrigerate or freeze whole blood prior to testing, as cold temperatures may activate or degranulate basophils. Maintain at room temperature (18-25°C) during transport.
- Hemolysis max
- 100
- Lipemia max
- 100
- Icterus max
- 50
- TAT
- 24–72 hours
- Order
- routine
What is this test, what does it measure, and why might my healthcare provider recommend it as part of my care?
The Baker's yeast triggered histamine release test is a specialized blood test that measures how your immune system responds to Baker's yeast (Saccharomyces cerevisiae). When your blood is exposed to yeast proteins, certain immune cells called basophils may release histamine. This test quantifies that histamine release to determine if you have an allergic sensitivity to yeast.
How is this test performed, what happens step by step during the procedure, and how long does it usually take?
A healthcare professional will draw a small sample of blood from your arm. The blood sample is then sent to a laboratory where it is mixed with Baker's yeast extracts. Technicians measure the amount of histamine released from your white blood cells in response to this exposure. The results are reported as a numerical value indicating the strength of your allergic reaction.
Do I need to prepare for this test, and are there special instructions about eating, drinking, or taking my medications beforehand?
Generally, no special preparation is needed. You can eat and drink normally before the test. However, inform your doctor about any medications you're taking, as some medications (especially antihistamines or corticosteroids) may affect test results. Your healthcare provider will give you specific instructions if any changes to your medications are needed before testing.
Reference range
Adult: 10-40 U/LN/A
No fasting required. Patients should discontinue antihistamines (H1 and H2 blockers), tricyclic antidepressants, and mast cell stabilizers for 5-7 days prior to testing as these may suppress histamine release. Corticosteroids may also interfere with results. Avoid the test during active infection or severe asthma exacerbation. Inform the laboratory of all current medications including herbal supplements.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test is primarily used to diagnose yeast allergies or sensitivities. Elevated histamine release indicates an IgE-mediated allergic response to Baker's yeast. Results can help explain symptoms such as digestive issues, skin reactions, respiratory problems, or chronic fatigue that may be related to yeast consumption. The test is also useful in evaluating patients with suspected baker's asthma (an occupational allergy in people who work with yeast-containing products).
Frequently asked questions
What do the results mean?
Is this test different from a food allergy test?
What foods contain Baker's yeast?
Does a positive result mean I must avoid all yeast?
Sources
- 1
- 2
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