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Blood Test Tracker

Penicillium chrysogenum IgE

Measures IgE antibodies to Penicillium, a common mold, in your blood. A detectable result means you are sensitized, which is not the same as a mold allergy.

AI-verified against cited sources. Awaiting expert reviewAlso called m1, m001LOINC 6212-5

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What it is

Penicillium is a common mold that likes damp places, and its spores float in the air indoors and outdoors. Some labs name this test for Penicillium chrysogenum and others for Penicillium notatum. It measures IgE, a type of antibody, to an extract of this mold (ImmunoCAP m1). Results come in kilounits per liter (kU/L), and many labs also print a class from 0 to 6. The test looks at the mold, not at allergy to penicillin, the antibiotic.

Why it matters

Mold allergy can cause nose, eye and chest symptoms. The American Academy of Allergy, Asthma & Immunology lists Penicillium among the most common allergy-causing molds. Studies find mold sensitization more often in people with asthma. Having IgE to Penicillium does not prove that mold is causing your symptoms, because some people have measurable IgE with no clinical sensitivity. Mold sensitization also often comes with allergy to other airborne allergens, such as pollen, dust mites and animal dander, so your symptom pattern and surroundings matter too.

If it’s high

A level above your lab's range means your immune system has made IgE against Penicillium. This is called sensitization. In some people it goes along with hay-fever-type symptoms or asthma, especially in damp places or when mold counts are high. Others have no symptoms. The number does not say how strong your symptoms are.

Common causes

  • Sensitization without symptoms
  • A true Penicillium (mold) allergy
  • Other airborne allergies, since many mold-sensitized people also react to pollen, dust mites or animal dander
  • IgE from other molds that share similar proteins (cross-reactivity)
  • A very high total IgE (above about 2,500 kU/L), which can cause a false-positive reading

What can help

  • Talk with a clinician about your symptom pattern, such as whether symptoms flare in damp indoor spaces or on days with high mold counts
  • Ask whether a skin test would add information, since skin tests and blood tests for mold do not always agree
  • Fixing leaks and damp spots and keeping indoor humidity below 60%, which are standard mold-avoidance steps

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: ARUP Laboratories, Mayo Clinic Laboratories, U.S. Food and Drug Administration, Journal of Allergy and Clinical Immunology, Allergy, Asthma & Immunology Research, American Academy of Allergy, Asthma & Immunology, MedlinePlus, National Library of Medicine, Thermo Fisher Scientific (Phadia).

ImmunoCAP IgE classes (ARUP labels and 0.10 cutoff; Mayo Clinic Laboratories class edges from 0.35 up)

  • Class 0: no significant level detectedbelow 0.1 kU/L
  • Class 0/1: clinical relevance undetermined0.1 to under 0.35 kU/L
  • Class 1: low0.35 to under 0.7 kU/L
  • Class 2: moderate0.7 to under 3.5 kU/L
  • Class 3: high3.5 to under 17.5 kU/L
  • Class 4: very high17.5 to under 50 kU/L
  • Class 5: very high50 to under 100 kU/L
  • Class 6: very high100 and above kU/L

What can affect your result

  • Season and local climate, since mold spore counts in the air generally rise in late summer and early autumn and fall in winter
  • Indoor dampness and poor ventilation, which can raise mold exposure
  • Other airborne allergies, such as pollen, dust mites and animal dander
  • Mold extracts vary in allergen content between manufacturers and batches
  • A very high total IgE (above about 2,500 kU/L) can cause false-positive results
  • The lab and test brand, because results from different systems are not directly comparable
  • Where a lab draws its cutoff (0.10 or 0.35 kU/L)
  • A very high total IgE (above about 2,500 kU/L) can cause false-positive results through nonspecific binding (Mayo Clinic Laboratories).
  • Antihistamines do not affect this blood test the way they affect skin-prick testing (NIAID 2010), but follow your clinician's instructions about any medicine before the test.
  • Mold extracts used for testing vary in quality and allergen content, and different labs and test brands give different numbers for the same blood sample.

When to talk to a clinician

Get urgent medical help for severe trouble breathing, wheezing or chest tightness that does not ease, or swelling of the lips or throat. Otherwise, talk with a clinician if you have a lasting cough, wheeze, stuffy nose or itchy eyes that seem tied to damp places or mold season, even if this result is in the usual range.

Questions you could ask

  • Are there other airborne allergens worth checking, such as dust mites or pollen?
  • Does this result have anything to do with a penicillin antibiotic allergy?
  • Do my symptoms follow damp places or high mold counts?
  • Would a skin test or tests for other molds add useful information?
  • Does this result change how we think about my asthma or nasal allergies?
  • My result is in the usual range but I still have symptoms around damp places. What should we look at next?

Questions people ask

Does a positive Penicillium IgE mean I am allergic to the antibiotic penicillin?

No. This test measures IgE to the Penicillium mold, not to the antibiotic penicillin. The test maker's allergen reference says there is no cross-reactivity between Penicillium sensitization and penicillin drug allergy. Penicillin drug allergy is checked with different tests. If you have questions about a penicillin allergy, ask your clinician.

Does a positive result mean mold is causing my symptoms?

Not on its own. Some people have measurable IgE to Penicillium and no symptoms, and many people with mold sensitization are also sensitized to other airborne allergens. Your clinician looks at the result with your symptom pattern, the season and your surroundings.

Why does my lab call it Penicillium notatum or Penicillium chrysogenum?

Both names are used for the same ImmunoCAP test (m1). Mayo lists it as Penicillium chrysogenum with Penicillium notatum as an alias, while ARUP lists it as Penicillium notatum with Penicillium chrysogenum as an alias.

Show the science and sources

For clinicians and researchers

Quantitative IgE to a Penicillium chrysogenum extract (ImmunoCAP m1; also labeled Penicillium notatum) by fluoroenzyme immunoassay. ARUP and Mayo both list LOINC 6212-5. The ImmunoCAP Specific IgE system reports up to 100 kUA/L with a limit of quantitation of 0.1 kUA/L, and its maker recommends a 0.35 kUA/L cutoff while telling each lab to set its own range (FDA review K173726). Penicillium is one of the four fungal genera most associated with allergy, with Alternaria, Cladosporium and Aspergillus, and mold sensitization is estimated at 3 to 10% in the general population. Natural mold extracts vary by strain, culture conditions and manufacturing, so extract-based results are less consistent than for many other allergens, and skin test and serum IgE results are often not directly comparable. IgE reactivity correlates better among closely related molds than among distant ones, monosensitization to fungi is rare, and specific IgE to fungi is often accompanied by IgE to other aeroallergens. Defined P. chrysogenum allergens include Pen ch 13 (alkaline serine protease) and Pen ch 18 (vacuolar serine protease); this marker measures the whole extract and does not report them (mold review 2015). Cutoffs and predictive values do not transfer between assay brands (NIAID 2010). Mayo notes false positives can occur above about 2,500 kU/L total IgE.

LOINC 6212-5 (primary), 112196-1. Specimen: serum.

Sources

  1. Allergen, Fungi and Molds, Penicillium notatum (ARUP test 0055080), ARUP Laboratories
  2. Penicillium chrysogenum, IgE, Serum (test ID PENL), Mayo Clinic Laboratories
  3. 510(k) Decision Memorandum K173726: ImmunoCAP Specific IgE (ImmunoCAP Allergen f447, rAra h 6, Peanut), U.S. Food and Drug Administration (2018)
  4. Guidelines for the diagnosis and management of food allergy in the United States: report of the NIAID-sponsored expert panel, Journal of Allergy and Clinical Immunology (2010)
  5. Allergy Blood Test, MedlinePlus, National Library of Medicine
  6. Mold Allergens in Respiratory Allergy: From Structure to Therapy, Allergy, Asthma & Immunology Research (2015)
  7. Mold Allergy, American Academy of Allergy, Asthma & Immunology
  8. m1 Penicillium chrysogenum (Allergen Encyclopedia), Thermo Fisher Scientific (Phadia)

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

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