{"id":"ige-ara-h-2","name":"Ara h 2 (peanut) IgE","shortName":"Ara h 2 IgE","aliases":["Ara h 2 IgE","rAra h 2","f423","Peanut Component Ara h 2, IgE","Allergen, Food, Peanut Component Ara h 2, IgE","Severe Peanut IgE Ara h 2","F423-IgE Ara h 2","Peanut Component Ara h 2","Peanut recombinant (rAra h) 2 IgE","ImmunoCAP f423","Ara h 2 (f423)"],"abbreviations":["f423","rAra h 2"],"loinc":[{"code":"58778-2","primary":true},{"code":"112866-9","primary":false}],"specimen":"serum","units":[{"ucum":"kU/L","display":"kU/L"}],"referenceRanges":[{"population":"Adults","low":0,"high":0.09,"unit":"kU/L","unitDisplay":"kU/L","note":"Mayo Clinic Laboratories and the UW Medicine test guide (ARUP performs the test) print under 0.10 kU/L as negative, and ARUP's own listing says 0.09 kU/L or lower. Mayo lists 0.10 to 0.34 kU/L as borderline and flags 0.70 and above, and its reference values apply to all ages. Quest's online directory tells users to rely on the range printed on their lab report. The ImmunoCAP maker suggests a 0.35 kUA/L cutoff for allergen IgE and tells each lab to set its own. Studies place the level that goes with true peanut allergy at different points, and in studies Ara h 2 IgE has been more accurate than whole-peanut IgE for telling peanut allergy from tolerance (Klemans 2015, Dang 2012). Results from different labs or test brands are not directly comparable.","sources":[{"title":"Peanut, IgE with Reflex to Peanut Components, IgE, Serum (test ID PEANT)","url":"https://www.mayocliniclabs.com/test-catalog/overview/64756","publisher":"Mayo Clinic Laboratories"},{"title":"Allergen, Food, Peanut Component Ara h 2, IgE (ARUP test 3021007)","url":"https://ltd.aruplab.com/Tests/Pub/3021007","publisher":"ARUP Laboratories"},{"title":"Severe Peanut IgE Ara h 2 (lab code RPTAH2)","url":"https://menu.labmed.uw.edu/view/RPTAH2","publisher":"UW Medicine Laboratory Medicine & Pathology","year":2026},{"title":"Peanut Component Panel (Quest test code 91681)","url":"https://testdirectory.questdiagnostics.com/test/test-detail/91681/?cc=MASTER","publisher":"Quest Diagnostics"},{"title":"510(k) Decision Memorandum K173726: ImmunoCAP Specific IgE (ImmunoCAP Allergen f447, rAra h 6, Peanut)","url":"https://www.accessdata.fda.gov/cdrh_docs/reviews/K173726.pdf","publisher":"U.S. Food and Drug Administration","year":2018},{"title":"Guidelines for the diagnosis and management of food allergy in the United States: report of the NIAID-sponsored expert panel","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC4241964/","publisher":"Journal of Allergy and Clinical Immunology","year":2010},{"title":"Diagnostic accuracy of specific IgE to components in diagnosing peanut allergy: a systematic review","url":"https://pubmed.ncbi.nlm.nih.gov/25226880/","publisher":"Clinical & Experimental Allergy","year":2015},{"title":"Increasing the accuracy of peanut allergy diagnosis by using Ara h 2","url":"https://pubmed.ncbi.nlm.nih.gov/22385632/","publisher":"Journal of Allergy and Clinical Immunology","year":2012}]}],"review":{"status":"ai-verified","label":"AI-verified against cited sources. Awaiting expert review","lastReviewed":"2026-10-03"},"summary":"Measures IgE to Ara h 2, a peanut seed protein. It is one of the peanut components most closely tied to true peanut allergy and strong reactions.","url":"https://bloodtesttracker.com/markers/ige-ara-h-2","notice":"Information, not medical advice. Ranges differ between labs, so the range on your own report is the one your result is judged against."}