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Outdoor mould spores pollen

Outdoor mould spores (Cladosporium species, Alternaria alternata) is airborne here from june to october, peaking July and August for Cladosporium, August and early September for Alternaria. Allergenic potency: high. No established food cross-reaction.

This is reference information, not a diagnosis and not a treatment plan. A pollen calendar cannot tell you what you are allergic to, and no page can clear a food as safe for you — only the label on the packet in your hand and the clinician who knows your history can do that. Anything beyond mild, short-lived symptoms in the mouth or nose — swelling that affects breathing or swallowing, hives away from the mouth, wheeze, vomiting or faintness — is an emergency question, not a reading question.

● peak weeks · ○ usually airborne. Typical mainland window from the national aerobiology monitoring programmes of the region · checked 2026-09-06

Where it grows here

These are not pollen at all: they are the spores of fungi living on dead plant material, and the same aerobiology traps that count pollen count them. Cladosporium is the single most abundant airborne biological particle of the northern summer, and Alternaria lives on senescing leaves, straw and crop residue, which ties it to the harvest.

When it is in the air

Spore counts build through the summer and peak far later than most people expect: Cladosporium through July and August, Alternaria in August and early September, both of them rising sharply during dry harvest weather and during grass cutting. Unlike pollen, spores are often released in larger numbers after a warm dry spell than after rain.

What it feels like

This is the one row on the calendar with a specific respiratory reputation: Alternaria sensitisation is repeatedly associated in the literature with more severe asthma and with asthma exacerbations, particularly in children and young adults, and particularly during high-spore late-summer weather. Symptoms often look more chest-led and less nose-led than pollen.

What it cross-reacts with

There is no established outdoor-mould food cross-reaction. Eating mould-ripened cheese or fermented food is a separate question from inhaling Alternaria spores, and one does not predict the other. Sensitisation to indoor moulds in a damp building is also a distinct problem with a distinct fix.

Related pollens: other fungi, and indoor moulds.

Foods: no established cross-reaction. That is a useful negative — a food reaction in someone sensitised to outdoor mould spores is not explained by the pollen and deserves its own assessment.

Named allergen molecules: Alt a 1 (the major Alternaria allergen), Cla h 8. These are the official WHO/IUIS names, and they are what a component-resolved blood test reports.

What actually helps

Spores are not in the CAMS pollen forecast, so no live number exists here. The practical markers are the situations rather than a figure: harvest, mowing, turning compost, handling straw or hay, working in a barn, raking wet leaves in autumn. Anyone whose asthma reliably steps up in late August should raise mould with the clinician managing it, because the treatment plan for a seasonal asthma trigger is not the same as for hay fever.

What gets misread

Late-August symptoms are almost always blamed on pollen. The pollen calendar is largely finished by then except for mugwort, while spore counts are at their highest — and an autumn worsening that follows leaf raking rather than a flowering plant is a strong hint that spores rather than pollen are involved.

Sources: Regulation (EU) No 1169/2011, Annex II · Commission Implementing Regulation (EU) No 828/2014 (gluten claims) · WHO/IUIS Allergen Nomenclature · season windows from the national aerobiology monitoring programmes of Estonia, Finland, Sweden, Denmark and Norway · cross-reaction patterns paraphrased from the allergy literature and EAACI material · checked 2026-09-06

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