Skip to content
Blood Test Tracker

Alternaria alternata IgE

Measures IgE antibodies to Alternaria, a common outdoor mold, in your blood. A detectable result means you are sensitized, which can go with mold allergy or asthma.

AI-verified against cited sources. Awaiting expert reviewAlso called m6, m006LOINC 6020-2

Check your result

Sex (optional)

Type your result to see where it falls.

Nothing you type here leaves your browser.

What it is

Alternaria is a common mold. Its spores float in the air outdoors, and in many temperate places spore counts peak from summer into fall. This test measures IgE to an extract of Alternaria alternata (ImmunoCAP m6). Some labs list it under the name Alternaria tenuis. Results come in kilounits per liter (kU/L), and many labs also print a class from 0 to 6.

Why it matters

Mold allergy can cause nose, eye and chest symptoms. Studies find mold sensitization more often in people with asthma, and it may be a risk factor for developing asthma. Having IgE to Alternaria does not prove that mold is causing your symptoms, because some people have measurable IgE with no clinical sensitivity. Your pattern of symptoms, the season and your surroundings matter too.

If it’s high

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

Common causes

  • Sensitization without symptoms
  • IgE from other molds or other allergen sources that share similar structures (cross-reactivity)
  • Other airborne allergies, since many mold-sensitized people also react to dust mites, animal dander, grass or weed pollen
  • A true Alternaria (mold) allergy
  • 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 outdoors in summer and fall or in damp indoor spaces
  • Ask whether a more specific mold test, such as Alt a 1 (the main Alternaria allergen), would add information
  • Fixing damp spots and visible mold indoors, since dampness and mold at home are linked to asthma problems in children

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: Mayo Clinic Laboratories, ARUP Laboratories, U.S. Food and Drug Administration, Journal of Allergy and Clinical Immunology, Allergy, Asthma & Immunology Research.

ImmunoCAP IgE classes (Mayo Clinic Laboratories wording)

  • Class 0: negativebelow 0.1 kU/L
  • Class 0/1: borderline or equivocal0.1 to under 0.35 kU/L
  • Class 1: equivocal0.35 to under 0.7 kU/L
  • Class 2: positive0.7 to under 3.5 kU/L
  • Class 3: positive3.5 to under 17.5 kU/L
  • Class 4: strongly positive17.5 to under 50 kU/L
  • Class 5: strongly positive50 to under 100 kU/L
  • Class 6: strongly positive100 and above kU/L

What can affect your result

  • Season and local climate, since Alternaria spore counts rise in warm months in many places
  • Other airborne allergies, such as dust mites, animal dander and pollen
  • 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
  • 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).
  • 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.

Slow. It usually shifts over months to years, not weeks.

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 the season or to damp places, 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?
  • Do my symptoms follow the mold season or damp places?
  • Would a more specific mold test, such as Alt a 1, 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 in mold season. What should we look at next?

Questions people ask

What is the difference between Alternaria IgE and Alt a 1 IgE?

This test uses an extract of the whole mold, which holds many proteins. Alt a 1 is the main allergen protein in Alternaria. A separate Alt a 1 test is more specific for true Alternaria sensitization, because a whole-mold extract can pick up IgE to proteins shared with other molds.

Does a positive result mean mold is causing my symptoms?

Not on its own. Some people have measurable IgE to Alternaria 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 Alternaria tenuis?

Some labs, including Mayo Clinic Laboratories and ARUP, list this test as Alternaria tenuis alongside Alternaria alternata. ARUP lists it as ImmunoCAP m6, the same code (m6, or M006) that Labcorp prints for Alternaria alternata.

Show the science and sources

For clinicians and researchers

Quantitative IgE to an Alternaria alternata extract (ImmunoCAP m6; Mayo lists the test as Alternaria tenuis) by fluoroenzyme immunoassay. The ImmunoCAP Specific IgE system reports up to 100 kUA/L, and its maker recommends a 0.35 kUA/L cutoff while telling each lab to set its own range (FDA review K173726). Natural mold extracts vary by strain, culture conditions and manufacturing, including in Alt a 1 content, so extract-based results are less consistent than for many other allergens. Alt a 1 is the major, species-specific allergen. In a study of 80 European patients, recombinant Alt a 1 identified 98% of patients with Alternaria allergy, and the review suggests it could stand in for the extract, although another study found 2 of 30 patients who reacted to MnSOD but not to Alt a 1 or Alt a 6; Alt a 6 (enolase) is a cross-reactive allergen. A Spanish multicenter study found that in over one-third of patients a positive in vivo result was not confirmed in vitro. Mold sensitization is estimated at 3 to 10% in the general population and 5 to 20% in people attending allergy clinics. Mayo flags class 2 and above (0.70 kU/L or more) and notes false positives can occur above about 2,500 kU/L total IgE.

LOINC 6020-2 (primary), 112157-3. Specimen: serum.

Sources

  1. Alternaria tenuis, IgE, Serum (test ID ALTN), Mayo Clinic Laboratories
  2. Allergen, Fungi and Molds, Alternaria alternata (tenuis) (ARUP test 0055001), ARUP Laboratories
  3. Mold Allergens in Respiratory Allergy: From Structure to Therapy, Allergy, Asthma & Immunology Research (2015)
  4. 510(k) Decision Memorandum K173726: ImmunoCAP Specific IgE (ImmunoCAP Allergen f447, rAra h 6, Peanut), U.S. Food and Drug Administration (2018)
  5. 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)

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

Related markers