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Blood Test Tracker

Cladosporium herbarum IgE

Shows whether your immune system has made IgE antibodies to Cladosporium herbarum, a common indoor and outdoor mold.

AI-verified against cited sources. Awaiting expert reviewAlso called m2, M002LOINC 6075-6

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What it is

Cladosporium herbarum is a common mold. It grows on plants and soil outdoors and in damp spots indoors, and it releases tiny spores into the air. Most people breathe in some mold spores every day. This test measures IgE, the type of antibody linked to allergic reactions, that your body has made against this mold. Sensitization means your body has made IgE antibodies to a substance. It does not always mean you are allergic.

Why it matters

IgE to molds like Cladosporium is linked to hay fever-type symptoms such as a stuffy nose, sneezing and itchy eyes. It is also linked to asthma. In people with asthma, being sensitized to molds has been linked to more severe asthma. A result can help you and your clinician work out whether mold may be one of your triggers. It can't show how much mold is in your home, and it can't show that mold is behind a particular symptom.

If it’s high

A result above your lab's usual range means your body has made IgE antibodies to this mold. Many people with this result have no symptoms. Others have a stuffy nose, sneezing, itchy eyes, cough or wheeze. Higher numbers are more often linked to symptoms, but they don't reliably predict how strong a reaction will be.

Common causes

  • An allergy-prone immune system (atopy), which often comes with other allergies such as pollen or dust mite
  • Everyday exposure to mold spores, which are found both outdoors and indoors
  • Time spent in damp or water-damaged buildings
  • A weak result of 0.10 to 0.34 kU/L, which labs treat as uncertain
  • Differences between lab methods, since mold test extracts are harder to standardize than most

What can help

  • Talk with your clinician about whether your symptoms fit this result
  • Ask whether steps to cut dampness at home, such as fixing leaks and ventilating bathrooms, make sense for you
  • Ask whether an allergy specialist could help sort out which triggers matter most

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: 0–0.1 kU/L. Source: Thermo Fisher Scientific, Labcorp, ARUP Laboratories, Quest Diagnostics, Thermo Fisher Scientific (Phadia), Journal of Allergy and Clinical Immunology, NIAID / Journal of Allergy and Clinical Immunology, World Allergy Organization Journal, Journal of Fungi, Clinical and Translational Allergy, Science of the Total Environment, Children's Minnesota.

ImmunoCAP class scale as printed by Quest and ARUP (cut points differ by about 0.01 between labs)

  • 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

  • Exposure: outdoor spore counts rise and fall with temperature, rain and humidity, and indoor exposure depends on dampness
  • Other allergies: people with IgE to other molds or allergens often show it here too
  • Lab method: results from different labs or assay systems may not be comparable, and mold extracts vary more than most
  • Medicines: antihistamines do not change this blood test, unlike skin prick testing
  • Very high total IgE can produce weak, nonspecific positive results.
  • Different assay systems give different numbers for the same blood sample, so compare results from the same lab and method.
  • Some labs reject samples that are hemolyzed (red cells broken), jaundiced (icteric) or lipemic (very fatty).

Antibody levels usually change slowly, over months to years.

When to talk to a clinician

Talk with a clinician if nose or chest symptoms keep coming back or get worse around damp places. Call your local emergency number for severe trouble breathing, or for wheeze or chest tightness that your usual treatment doesn't ease.

Questions you could ask

  • If my result and my symptoms don't match, would a repeat test or a different type of test help?
  • Could mold be one of my triggers, given when my symptoms happen?
  • Would an allergy specialist or skin testing help sort out my triggers?
  • Is it worth checking for other molds or allergens at the same time?

Questions people ask

Why does my report say Hormodendrum?

Hormodendrum is an older name for the Cladosporium group of molds, and some labs still use it. ARUP, for example, lists its Cladosporium herbarum test under that name. It is the same type of test.

Does a positive result mean mold in my home is making me sick?

No. The test shows whether your immune system has made IgE to this mold. It doesn't measure mold in your home, and it can't show that mold is causing a specific symptom. Your clinician looks at the result together with your symptoms and when they happen.

How should I read a result of 0.10 to 0.34 kU/L?

Labs treat this low zone differently. Many call it class 0/1, and ARUP says its clinical relevance is undetermined. Ask your clinician how to read it alongside your symptoms.

Show the science and sources

Units

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

For clinicians and researchers

ImmunoCAP m2 is a fluorescent enzyme immunoassay for IgE to a Cladosporium herbarum extract, with a manufacturer-stated quantitative range of 0.1 to 100 kUA/L (above 100 is printed as >100). ARUP reports it as 'Hormodendrum', an older genus name for Cladosporium. Fungal extracts show the greatest variability of any allergen source, because spores versus mycelium, growth conditions and extraction method all change allergen content, so a negative extract result does not fully exclude sensitization. Allergens cross-reactive with Alt a 1 occur in Alternaria and its relatives but not in Cladosporium, so Alternaria IgE does not stand in for Cladosporium IgE. Sensitization to fungi is associated with more severe asthma, and as with every specific IgE test, a positive result shows sensitization rather than clinical allergy. ARUP labels 0.10 to 0.34 kU/L as clinical relevance undetermined, while other labs call it equivocal or very low. The class tables differ slightly between labs, so use the class your own report prints.

LOINC 6075-6 (primary), 112138-3. Specimen: serum.

Sources

  1. Allergens, Inhalants, Comprehensive Profile IgE (test 0055312), ARUP Laboratories
  2. Allergens, Mold Profile, Southeast Comprehensive (test 0055387), ARUP Laboratories
  3. M002-IgE Cladosporium herbarum (test 602462), Labcorp
  4. Sample patient report: Allergens with Component Reflex, Area 20 (test 607120), Labcorp (2021)
  5. ImmunoCAP Specific IgE Blood Test: Allergy Test List (interpretation table and test codes), Quest Diagnostics (2017)
  6. ImmunoCAP Specific IgE blood test results: Interpretation (respiratory results interpretation guide), Thermo Fisher Scientific (Phadia) (2023)
  7. ImmunoCAP Mold and Yeast Allergens (Thermo Fisher product page; lists m2 Cladosporium herbarum; measuring range 0.1 to 100 kUA/L), Thermo Fisher Scientific
  8. ImmunoCAP allergy: Change to Reference Interval Interpretation, UR Medicine Labs, University of Rochester Medical Center (2022)
  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. 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)
  11. IgE allergy diagnostics and other relevant tests in allergy, a World Allergy Organization position paper, World Allergy Organization Journal (2020)
  12. Problems Encountered Using Fungal Extracts as Test Solutions for Fungal Allergy Diagnosis, Journal of Fungi (2023)
  13. Fungal allergy in asthma: state of the art and research needs, Clinical and Translational Allergy (2014)
  14. A systematic review of outdoor airborne fungal spore seasonality across Europe and the implications for health, Science of the Total Environment (2022)
  15. Allergen IgE (laboratory test manual entry; class table and reporting rules), Children's Minnesota (2018)

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

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