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Ash pollen

Ash (Fraxinus excelsior) is airborne here from april to may, peaking late April into May, overlapping the birch peak almost exactly. Allergenic potency: moderate. 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

Common ash is a tall forest and parkland tree, most abundant in the western and southern parts of the region and in Denmark and southern Sweden. Its numbers have fallen sharply because of ash dieback, the fungal disease that has swept through European ash over the last two decades, which is slowly reducing how much ash pollen is in the air here.

When it is in the air

Ash flowers in late April and May, on top of the birch season. That overlap is why ash allergy is underdiagnosed in the north: the symptoms are attributed to birch, which is airborne in far greater quantity at the same time and is the obvious suspect.

What it feels like

Ordinary rhinoconjunctivitis, indistinguishable in the chair from birch. What separates them is a blood or skin test for the specific allergen, and in practice that test is only ordered when it will change something — for example, before starting immunotherapy aimed at the right tree.

What it cross-reacts with

Ash is in the olive family, and its major allergen belongs to the Ole e 1-like protein group. That means ash allergy cross-reacts with olive pollen — a serious allergen in southern Europe but not a factor here — and with privet and lilac. There is no established ash-to-food syndrome. A less obvious relative is ribwort plantain, whose major allergen is in the same protein family, which is one route to symptoms that continue past the tree season into the summer.

Related pollens: olive, privet and lilac — the olive family — and plantain.

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

Named allergen molecules: Fra e 1 (an Ole e 1-like protein). These are the official WHO/IUIS names, and they are what a component-resolved blood test reports.

What actually helps

If spring symptoms clearly start before birch and continue after it, ash is one of the reasonable explanations and is worth naming when you see a clinician. It also matters for anyone travelling south in spring: an ash-allergic northerner can have a bad time in an olive-growing region without ever having reacted to an olive tree at home.

What gets misread

Ash is often assumed to be irrelevant this far north. It is not — it is simply hidden underneath birch. The other misreading runs the other way: eating olives has nothing to do with olive pollen allergy, and ash allergy is not a reason to avoid them.

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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