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Blood Test Tracker

Pistachio IgE

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

AI-verified against cited sources. Awaiting expert reviewAlso called f203, F203LOINC 7613-3

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What it is

Pistachio is a tree nut, the seed of the Pistacia vera tree. This test measures IgE, the antibody type linked to allergic reactions, that your body has made against pistachio. Pistachio is a close relative of cashew, and both are in the same plant family as mango, so IgE to one often shows up for the other. Sensitization means your body has made IgE antibodies to a substance. It does not always mean you are allergic.

Why it matters

Tree nut allergy can cause reactions that range from itching in the mouth and hives to a serious reaction called anaphylaxis. A positive pistachio result shows that IgE is present. It does not prove you are allergic. In one small study of children sensitized to both cashew and pistachio, only about one in three reacted to pistachio in a supervised food challenge. 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 pistachio. It is more likely to match a true pistachio allergy if you have had symptoms soon after eating pistachios. 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 pistachio allergy, with symptoms soon after eating pistachios
  • Sensitization without symptoms, which is common with food IgE tests
  • Cross-reaction with cashew, a close relative, so a cashew allergy often comes with a positive pistachio result
  • Cross-reaction with other tree nuts such as walnut, or with pink peppercorn
  • 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 pistachios, talk with your clinician before eating them again
  • Ask whether an allergy specialist could test cashew and other tree nuts and decide if a supervised food challenge makes sense
  • 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, World Allergy Organization Journal, Clinical and Translational Allergy, Journal of Allergy and Clinical Immunology, Clinical and Experimental Allergy, 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

  • Cashew: IgE to cashew and pistachio often occur together, and in one study the two clustered closely in challenge results
  • Age and how long you have avoided pistachio can change how a given number relates to symptoms
  • Other tree nuts and pink peppercorn, which can cross-react
  • Lab method: results from different labs or assay systems may not be comparable
  • 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 pistachios or cashews, 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 pistachios or cashews.

Questions you could ask

  • How should I read this result if I've never had a reaction to pistachios?
  • Does this result fit the symptoms I've had after eating pistachios?
  • Should I see an allergy specialist, and would testing for cashew or other tree nuts help?
  • Is a supervised food challenge appropriate for me?
  • What should my plan be if I have a reaction?

Questions people ask

I react to cashew. Does a positive pistachio result mean I react to pistachio too?

Not always. Cashew and pistachio are close relatives, so IgE to one often shows up for the other. In one study of children sensitized to both, about one in three reacted to pistachio in a supervised food challenge. An allergy specialist can help sort out which nuts are safe. If you've had a reaction, talk with your clinician before trying nuts again.

Can I have a negative result and still be allergic?

It's uncommon, but yes. Undetectable IgE can happen in people with an IgE-mediated food allergy. If your history strongly suggests a reaction, your clinician may suggest a supervised food challenge before you eat the food again.

Does a positive pistachio result mean I should avoid mango?

Cashew, pistachio and mango are in the same plant family, but reactions to mango are less common. In a small study of cashew- and pistachio-sensitized children, none reacted to mango in a challenge. Your clinician or an allergy specialist can advise what is right for you.

Show the science and sources

Units

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

For clinicians and researchers

ImmunoCAP f203 is a fluorescent enzyme immunoassay for IgE to a pistachio (Pistacia vera) extract. Five pistachio allergens are registered with WHO/IUIS: Pis v 1 (2S albumin, major), Pis v 2 (11S globulin, major), Pis v 3 (7S vicilin), Pis v 4 (manganese superoxide dismutase) and Pis v 5 (11S globulin). Thermo Fisher notes that no quantitative pistachio component test is available, and that cashew Ana o 3 (2S albumin, roughly 66 to 70% sequence match to Pis v 1) has proven useful when pistachio allergy is investigated. Pistachio, cashew and mango belong to Anacardiaceae. In the IDEAL follow-up study, 98% of cashew-sensitized children were also sensitized to pistachio, but pistachio sensitization was clinically relevant in only 34% on double-blind challenge (n=29), and none reacted to mango, so the authors recommend a pistachio challenge in children sensitized to both. Pis v 3 cross-reacts with cashew Ana o 1 (Willison 2008). The Pronuts challenge study found strong correlations between cashew and pistachio allergy. In the NIAID 2010 summary table, tree nut versus other tree nut IgE cross-reactivity was about 92% with clinical reactivity of 12% to 37% (not systematically confirmed by blinded challenge), and cashew and pistachio showed higher IgE correlations. 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 7613-3 (primary), 112102-9. Specimen: serum.

Sources

  1. F203-IgE Pistachio Nut (test 602486), Labcorp
  2. Sample patient report: F203-IgE Pistachio Nut (test 602486), Labcorp
  3. Allergen, Food, Pistachio (test 0055447), 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: f203 Pistachio, 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. IgE allergy diagnostics and other relevant tests in allergy, a World Allergy Organization position paper, World Allergy Organization Journal (2020)
  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. Low percentage of clinically relevant pistachio nut and mango co-sensitisation in cashew nut sensitised children, Clinical and Translational Allergy (2017)
  11. Defining challenge-proven coexistent nut and sesame seed allergy: A prospective multicenter European study, Journal of Allergy and Clinical Immunology (2020)
  12. Pistachio vicilin, Pis v 3, is immunoglobulin E-reactive and cross-reacts with the homologous cashew allergen, Ana o 1, Clinical and Experimental Allergy (2008)
  13. 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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