Scallop F338 IgE Biomarker Testing
It measures IgE antibodies to scallop to assess allergy risk, with results you can review in PocketMD and order through Vitals Vault via Quest labs.
With Vitals Vault, you have access to a comprehensive range of biomarker tests.
A Scallop F338 IgE test is a blood test that looks for IgE antibodies your immune system may make in response to scallop. It is used to assess whether your symptoms after eating scallop could be related to an IgE-mediated food allergy.
This test does not “prove” you are allergic on its own. It measures sensitization (your immune system recognizes the allergen), which has to be interpreted alongside your history, timing of symptoms, and sometimes additional testing.
If you have had hives, swelling, wheezing, vomiting, or other rapid symptoms after eating scallop or mixed seafood, testing can help you and your clinician decide what to avoid, what to challenge, and what to recheck over time.
Do I need a Scallop F338 IgE test?
You may want this test if you have symptoms within minutes to a few hours after eating scallop, such as hives, itching, lip or tongue swelling, throat tightness, coughing, wheezing, abdominal cramping, or vomiting. A reaction that happens quickly after exposure is the classic pattern for IgE-mediated allergy, and that is the scenario where a specific IgE result is most useful.
This test can also be helpful if you have a history of shellfish reactions but you are not sure which type triggered it, or if you avoid scallop because of a past reaction and want a data point to discuss next steps with your clinician. If you have eczema, allergic rhinitis, or asthma, you can have higher background IgE and more “false-positive” sensitizations, so your symptom story matters even more.
You typically do not need scallop IgE testing for slow, non-specific symptoms like fatigue, brain fog, or chronic bloating without a clear, repeatable link to scallop. In those cases, other evaluations are usually more informative.
Testing is meant to support clinician-directed care and risk assessment, not to self-diagnose or to decide on food challenges without guidance.
This is a CLIA laboratory blood test for allergen-specific IgE; results should be interpreted with your clinical history and are not a standalone diagnosis of food allergy.
Lab testing
Order Scallop F338 IgE and schedule your blood draw when it works for you.
Schedule online, results typically within about a week
Clear reporting and optional clinician context
HSA/FSA eligible where applicable
Get this test with Vitals Vault
With Vitals Vault, you can order Scallop F338 IgE directly and complete your blood draw through a national lab network. This is useful when you want a clear, documented result to bring to your clinician, especially if you are deciding whether scallop needs strict avoidance.
After your result posts, PocketMD can help you put it into context: how IgE relates to reaction risk, what “class” or kU/L values generally imply, and what follow-up questions to ask based on your symptom timing and severity.
If your situation suggests broader mapping, you can add companion testing (for example, other shellfish or related allergy markers) so you are not making decisions from a single data point. You can also use repeat testing to track trends over time when your clinician recommends it.
- Order online and schedule a local blood draw
- PocketMD guidance for next-step questions and retest planning
- Results you can share with your clinician for clinical context
Key benefits of Scallop F338 IgE testing
- Helps assess whether scallop is a plausible trigger for rapid-onset allergic symptoms.
- Distinguishes IgE-mediated sensitization from non-allergic food intolerance patterns.
- Supports safer avoidance decisions when your reaction history is unclear or mixed seafood was involved.
- Provides a baseline value you can trend if your clinician recommends retesting over time.
- Helps guide whether additional shellfish or fish IgE tests may be worth adding for a broader picture.
- Can reduce uncertainty before discussing supervised oral food challenge or reintroduction planning with a clinician.
- Creates a clear lab record you can review in PocketMD and share for coordinated care.
What is Scallop F338 IgE?
Scallop F338 IgE is an allergen-specific immunoglobulin E (IgE) blood test. It measures the amount of IgE in your blood that binds to scallop proteins (the allergen source labeled “F338” in many lab systems).
IgE is the antibody class involved in immediate-type allergic reactions. If you are sensitized, your immune system has made IgE that recognizes scallop. When scallop proteins are eaten and absorbed, they can cross-link IgE on mast cells and basophils, which may trigger release of histamine and other mediators. That is what can lead to symptoms like hives, swelling, wheeze, or vomiting.
A key point is that sensitization is not the same as clinical allergy. Some people have measurable scallop-specific IgE but tolerate scallop without symptoms, while others react at low levels. Your history (what you ate, how much, how fast symptoms started, and what happened) is essential for interpretation.
How this differs from total IgE
Total IgE is a broad measure of IgE across many triggers and can be elevated in eczema, asthma, parasitic infections, and other allergic conditions. Scallop F338 IgE is targeted to one food and is more actionable for scallop-specific questions.
Shellfish cross-reactivity in real life
Shellfish allergy often involves cross-reactivity within groups, but it is not uniform. A positive scallop IgE does not automatically mean you will react to shrimp, crab, or lobster, and the reverse is also true. If you react to one shellfish, your clinician may consider testing additional shellfish to clarify your personal pattern.
What do my Scallop F338 IgE results mean?
Low or undetectable Scallop IgE
A low or undetectable result generally means scallop-specific IgE was not found at the lab’s detection threshold. This makes an IgE-mediated scallop allergy less likely, but it does not fully rule it out, especially if your reaction was convincing or happened long ago. If you had a severe reaction history, your clinician may still recommend caution and may consider skin testing or a supervised challenge rather than home reintroduction.
In-range / negative range Scallop IgE
Many labs report a reference interval where results below a cutoff are considered negative. In that range, your immune system is not showing meaningful IgE binding to scallop on this assay, which often aligns with tolerance. If you still have symptoms after eating scallop, it raises the possibility of a non-IgE mechanism, a reaction to another ingredient (for example, sauces or cross-contact), or a different seafood trigger.
Elevated Scallop IgE
An elevated result indicates sensitization to scallop and increases the likelihood that scallop could trigger an IgE-mediated reaction. Higher values can correlate with higher probability of clinical allergy in some settings, but the number alone cannot predict reaction severity. Your next steps usually depend on your history: if you have had systemic symptoms, strict avoidance and an allergy plan are common; if your history is unclear, your clinician may recommend additional testing or supervised challenge rather than guessing.
Factors that influence Scallop IgE results
Your overall allergic background matters: eczema, asthma, and multiple environmental allergies can raise the chance of positive specific IgE results that do not always match symptoms. Recent exposure is not required for a positive result, and IgE can persist for months to years, although levels may change over time. Cross-reactivity with other shellfish proteins can also contribute to a positive test. Finally, different labs and methods can have slightly different cutoffs, so it helps to trend results using the same lab when possible.
What’s included
- SCALLOP (F338) IGE
Frequently Asked Questions
Do I need to fast for a Scallop F338 IgE blood test?
Fasting is not usually required for allergen-specific IgE testing. If you are combining this with other labs (like lipids or glucose), those may have fasting requirements, so follow the instructions for your full order.
What does “F338” mean on my scallop IgE result?
F338 is a lab coding label used to identify the specific allergen source (scallop) in many immunoassay systems. It helps standardize ordering and reporting, but the clinical meaning is simply “scallop-specific IgE.”
If my scallop IgE is positive, does that mean I will have anaphylaxis?
No. A positive result means sensitization and a higher likelihood of allergy, but it cannot predict how severe a reaction would be. Your past reactions, asthma control, and other factors are more informative for risk planning, so review the result with a clinician.
Can I have a negative scallop IgE and still react to scallop?
Yes, although it is less common for true IgE-mediated allergy. You might react to another seafood in the meal, to cross-contact, or to a non-IgE mechanism. If you had a convincing immediate reaction, do not use a negative test as permission to reintroduce without clinical guidance.
How is scallop IgE different from IgG food tests?
IgE testing is designed to evaluate immediate-type allergy risk. IgG or IgG4 food panels often reflect exposure and tolerance rather than allergy, and they are not used to diagnose IgE-mediated food allergy. If your concern is hives, swelling, wheeze, or rapid vomiting after scallop, IgE is the relevant antibody class.
When should I retest scallop IgE?
Retesting is usually considered when you are tracking whether sensitization is changing over time or when you are reassessing avoidance with your clinician. Many people retest in 6–12 months if there is a clinical reason, but timing should be individualized based on your history and risk.
Should I test other shellfish if scallop IgE is high?
Often, yes. Because shellfish allergies can overlap, your clinician may recommend testing additional shellfish (and sometimes fish) to clarify what you should avoid and what might be safe. The best next test depends on what you eat, what you reacted to, and your local dietary patterns.