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Blood Test Tracker

Soybean IgE

Shows whether your immune system has made IgE antibodies to soy. This is called sensitization and doesn't always mean a soy allergy.

AI-verified against cited sources. Awaiting expert reviewAlso called f14, F014LOINC 6248-9

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What it is

Soybeans are a legume used in tofu, soy milk, soy sauce, edamame and many packaged foods. This test measures IgE, the antibody type linked to allergic reactions, that your body has made against soy. In children, soy allergy often fades with time. In adults who are allergic to birch pollen, a positive soy result can come from a soy protein that looks like the birch allergen, and it often causes only mild mouth symptoms. Sensitization means your body has made IgE antibodies to a substance. It does not always mean you are allergic.

Why it matters

Soy is one of the major food allergens, and soy allergy can cause reactions that range from hives and stomach upset to a serious reaction called anaphylaxis. A positive soy result shows that IgE is present. It does not prove you are allergic, and many sensitized people eat soy without trouble, especially people with peanut allergy. A negative result doesn't fully rule out an allergy either. Your history of reactions matters most, and an allergy specialist may use a supervised food challenge to settle the question.

If it’s high

A result above your lab's usual range means your body has made IgE antibodies to soy. It is more likely to match a true soy allergy if you have had symptoms soon after eating soy. The number alone can't tell how strong a reaction would be, and no blood test can predict how severe a future reaction will be.

Common causes

  • A true soy allergy, with symptoms soon after eating soy
  • Sensitization without symptoms, which is common with food IgE tests
  • Cross-reaction with peanut, which is common on blood tests but much less common when soy is actually eaten
  • Birch pollen allergy, because a soy protein (Gly m 4) looks like the main birch allergen. It can cause mouth itching or other symptoms, mostly with lightly processed soy such as soy milk.
  • A weak result of 0.10 to 0.34 kU/L, which labs treat as uncertain

What can help

  • If you have had symptoms after eating soy, talk with your clinician before eating it again
  • Ask whether soy component tests (such as Gly m 4, Gly m 5 and Gly m 6) could show whether birch pollen or a true soy allergy is behind the result
  • Ask whether re-testing or a supervised food challenge could show if you have outgrown a childhood soy allergy
  • Ask for a written plan for what to do if you have a reaction

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: 0–0.09 kU/L. Source: Labcorp, ARUP Laboratories, Quest Diagnostics, Thermo Fisher Scientific (Phadia), NIAID / Journal of Allergy and Clinical Immunology, Journal of Allergy and Clinical Immunology, MedlinePlus (National Library of Medicine).

ImmunoCAP class scale as printed by Quest and ARUP (labs differ on which class an exact edge value falls in)

  • Class 0: absent or undetectablebelow 0.1 kU/L
  • Class 0/1: very low level, relevance uncertain0.1 to under 0.35 kU/L
  • Class 1: low level0.35 to under 0.7 kU/L
  • Class 2: moderate level0.7 to under 3.5 kU/L
  • Class 3: high level3.5 to under 17.5 kU/L
  • Class 4: very high level17.5 to under 50 kU/L
  • Class 5: very high level50 to under 100.01 kU/L
  • Class 6: very high level100.01 and above kU/L

Labcorp class scale (ImmunoCAP, as printed on Labcorp reports)

  • Class 0: negativebelow 0.1 kU/L
  • Class 0/I: equivocal or low0.1 to under 0.32 kU/L
  • Class I: low0.32 to under 0.56 kU/L
  • Class II: moderate0.56 to under 1.41 kU/L
  • Class III: high1.41 to under 3.91 kU/L
  • Class IV: very high3.91 to under 19.01 kU/L
  • Class V: very high19.01 to under 100.01 kU/L
  • Class VI: very high100.01 and above kU/L

What can affect your result

  • Age: most soy allergy that starts in early childhood fades. In one US clinic study about 7 in 10 children had outgrown it by age 10, and a higher peak soy IgE was linked to a lower chance of outgrowing it.
  • Birch pollen allergy, which can raise soy IgE through a look-alike protein (Gly m 4)
  • Processing: fermented soy such as soy sauce and miso is less allergenic than soy milk or tofu
  • Peanut: IgE overlaps are common on blood tests, but clinical reactions to soy in peanut-allergic people are much less common
  • Lab method: results from different labs or assay systems may not be comparable
  • The soy extract can miss the birch-related soy protein (Gly m 4), so a negative result may not rule out a reaction in people with birch pollen allergy (Thermo Fisher).
  • Results from different labs and test brands are not directly comparable, so compare results from the same lab and method (NIAID 2010).
  • Labs may reject samples that are hemolyzed (red cells broken), jaundiced (icteric) or lipemic (very fatty). ARUP lists all three as unacceptable.
  • MedlinePlus notes that some medicines, such as antihistamines, may matter before an allergy blood test. Tell your clinician about everything you take and ask them what applies to you.

Antibody levels usually change slowly, over months to years.

When to talk to a clinician

Call your local emergency number if, soon after eating soy, you have trouble breathing, throat tightness, swelling of the lips or tongue, repeated vomiting, dizziness or fainting. See a clinician soon if you get hives, itching or stomach upset after eating soy.

Questions you could ask

  • How should I read this result if I've never had a reaction to soy?
  • Does this result fit the symptoms I've had after eating soy?
  • Could my birch pollen or peanut allergy explain this result?
  • Would a soy component test or a supervised food challenge help?
  • What should my plan be if I have a reaction?

Questions people ask

My child has a positive soy result. Will they outgrow it?

Many children do. In one US clinic study, about 7 in 10 children with soy allergy had outgrown it by age 10, and lower soy IgE levels were linked with a better chance of outgrowing it. Each child is different. Your clinician can say when re-testing or a supervised food challenge makes sense.

I'm allergic to peanut and my soy test is positive. Do I have to avoid soy?

Not necessarily. Peanut and soy are both legumes, and IgE to one often shows up for the other, but in studies only about 3% to 5% of people with peanut allergy reacted to soy when it was tested by food challenge. Talk with your clinician before changing what you eat.

Why do I react to soy milk but not soy sauce?

Heating and fermenting change soy proteins. In people whose reaction comes from birch pollen allergy, lightly processed soy such as soy milk is more likely to cause symptoms, and cooked or fermented soy is less likely to. An allergy specialist can explain what applies to you.

Show the science and sources

Units

  • 1 kU/L = 1 kU/L
  • 1 kU/L = 1 UA/mL

For clinicians and researchers

ImmunoCAP f14 is a fluorescent enzyme immunoassay for IgE to a soybean (Glycine max) extract. Eight soy allergens are registered with WHO/IUIS (Gly m 1 to Gly m 8). Gly m 5 (7S globulin), Gly m 6 (11S globulin) and Gly m 8 (2S albumin) are stable storage proteins linked to primary soy allergy. In a European study of 30 people, 86% of those with anaphylaxis were sensitized to Gly m 5 and Gly m 6 versus 33% of those with mild symptoms, but adult studies have not consistently shown this association. Gly m 4, a PR-10 protein homologous to birch Bet v 1, drives soy reactions in birch-sensitized people, usually with soy milk or lightly processed soy. It is labile and scarce in extracts, so extract IgE and skin tests can be falsely negative in these patients (Thermo Fisher). In the NIAID 2010 summary table, peanut versus soy showed IgE cross-reactivity of 19% to 79% but clinical cross-reactivity of 3% to 5% (a lupine challenge reported 28% to 30%). In a US referral cohort (Savage 2010), Kaplan-Meier resolution of soy allergy was 25% by age 4, 45% by age 6 and 69% by age 10, and by age 6 tolerance was reached by 59%, 53%, 45% and 18% of children with peak soy IgE under 5, 5 to 9.9, 10 to 49.9 and over 50 kUA/L. Sensitization alone does not define food allergy, and undetectable IgE occasionally occurs in IgE-mediated food allergy, so a supervised oral food challenge remains the reference standard.

LOINC 6248-9 (primary), 112121-9. Specimen: serum.

Sources

  1. F014-IgE Soybean (test 602457), Labcorp
  2. Sample patient report: F014-IgE Soybean (test 602457), Labcorp
  3. Allergen, Food, Soybean (test 0055031), ARUP Laboratories
  4. ImmunoCAP Specific IgE Blood Test: Allergy Test List (interpretation table and test codes), Quest Diagnostics (2017)
  5. Your quick guide to using ImmunoCAP Specific IgE testing, Thermo Fisher Scientific (Phadia)
  6. Allergen Encyclopedia: f14 Soybean, Thermo Fisher Scientific (Phadia)
  7. Guidelines for the Diagnosis and Management of Food Allergy in the United States: Report of the NIAID-Sponsored Expert Panel, NIAID / Journal of Allergy and Clinical Immunology (2010)
  8. The natural history of soy allergy, Journal of Allergy and Clinical Immunology (2010)
  9. Prevalence of allergic sensitization in the United States: results from the National Health and Nutrition Examination Survey (NHANES) 2005-2006, Journal of Allergy and Clinical Immunology (2014)
  10. Allergy Blood Test, MedlinePlus (National Library of Medicine)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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