Alternaria mould allergy
Sneezing at harvest time, or on warm, windy evenings when the pollen count says low? Alternaria is an outdoor mould whose spores fill the air in summer and early autumn. Our test checks for IgE sensitisation to two Alternaria proteins as part of 300 allergens and allergen components, including indoor moulds, mites and pollen.
- Group
- Moulds and yeasts
- Season
- Mainly June to October in central Europe, peaking in July and August
- Also known as
- Alternaria alternata, mould allergy, mold allergy, Alt a 1, mould spores
Where you meet it
- Fields, grain crops and harvest dust
- Decaying leaves, compost and garden soil
- Outdoor air on warm, dry, windy days
- Occasionally indoors on damp window frames and wallpaper
What Alternaria is
Alternaria alternata is a mould that grows on plants, soil and crops. Its spores are released in large numbers on warm, dry, windy days, especially around harvest, and they are a well-known outdoor allergen. Its main allergen is called Alt a 1.
Unlike pollen, spore counts are often highest in the afternoon and evening and can stay high into autumn. That makes Alternaria easy to miss if you only follow pollen forecasts.
What people commonly report
Reports look like hay fever: sneezing, runny or blocked nose and itchy eyes, often in late summer. Alternaria sensitisation is also linked in research to asthma, so some people notice coughing or wheezing.
If your symptoms overlap with grass or mugwort season, a panel that tests mould alongside pollen helps separate them.
- Sneezing around fields or during harvest
- Symptoms when raking leaves or turning compost
- Cough or wheeze on warm, windy days
Outdoor and indoor mould
Alternaria is mainly an outdoor mould. Damp homes are more often home to others, such as Aspergillus, Penicillium and Cladosporium. A sensitisation to one mould does not mean you react to all of them, which is why the panel lists them separately.
If your home has visible mould, it is worth fixing whatever your result shows. That is about the building, not about a diagnosis.
How the test checks Alternaria
The lab measures IgE to two Alternaria alternata proteins in your finger-prick sample as part of 300 allergens and allergen components. Aspergillus fumigatus, Cladosporium and Penicillium are on the same panel, alongside pollens and house dust mite.
A positive result shows sensitisation, not a confirmed allergy. Each value gets a class from Negative to Very high, a pattern to discuss with a doctor, especially if you have chest symptoms.
- Alt a 1: the main Alternaria allergen, specific to Alternaria and close relatives
- Alt a 6: enolase, a protein shared by many moulds
Known cross-reactions
- Other moulds
- Some mould proteins overlap, such as enolase (Alt a 6), but sensitisation to Alternaria does not mean sensitisation to Aspergillus, Penicillium or Cladosporium. The panel lists each one separately.
Sources
- Alternaria alternata allergens: Markers of exposure, phylogeny and risk of fungi-induced respiratory allergy. Environment International, 2016.
- EAACI Molecular Allergology User's Guide 2.0. Pediatric Allergy and Immunology (EAACI), 2023.
Page last updated
300 allergens. One test.
A finger-prick sample at home, sent by post. A detailed lab report typically 5 days after the lab receives your sample, and our plain-English guide to reading it. €300, €1 per allergen.
Questions
When is mould spore season?
For Alternaria in central Europe, spore counts are highest from about June to October, peaking in July and August. Warm, dry, windy days and harvest time push them up.
Is Alternaria the black mould in my bathroom?
Usually not. Alternaria lives mostly outdoors. Bathroom and damp-wall moulds are more often Cladosporium, Aspergillus or Penicillium. The panel includes Cladosporium, Aspergillus fumigatus and Penicillium as well as Alternaria, so you can see which ones your blood shows IgE to.
Does a positive mould result mean my home is mouldy?
No. The test measures IgE in your blood, not mould in your home. Alternaria exposure is mostly outdoors. If you suspect damp at home, that needs a look at the building.