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Willow pollen

Willow (Salix species) is airborne here from april to may, peaking late April into early May. 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

Willows are everywhere in this region — goat willow in scrub and clearings, osier along ditches, dwarf willows in the north — and the silver-grey catkins are the first obvious flower of the northern spring. Willow is mainly insect-pollinated, which is unusual for a tree that causes hay fever, and that changes how it behaves in the air.

When it is in the air

The willow window is short: a couple of weeks from mid-April into early May in the Baltic and southern Finland, later going north. It sits exactly on top of the birch season, which is the practical problem — very few people can tell, from symptoms alone, which of the two is responsible during the last week of April.

What it feels like

Willow tends to cause milder and more variable symptoms than the wind-pollinated trees, and it affects people who work near it — beekeepers, gardeners, foresters — more than the general population, because insect-pollinated pollen stays close to the plant.

What it cross-reacts with

Willow does not have a recognised food cross-reaction syndrome, and it is not part of the birch PR-10 group. It does share allergens with poplar and aspen, its relatives in the same family. If a test comes back positive for willow but the symptom diary points at late April, birch is usually the one doing the work, because birch pollen is airborne in far greater quantity at the same moment.

Related pollens: poplar and aspen, which share the willow family.

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

Named allergen molecules: Sal k-type pollen proteins; no single dominant molecule in routine testing. These are the official WHO/IUIS names, and they are what a component-resolved blood test reports.

What actually helps

For most people willow needs no separate strategy: whatever is being done for birch covers the same fortnight. If symptoms are clearly worst while working close to flowering willow and mild otherwise, that is worth reporting to a clinician, because occupational exposure is treated differently from a general pollen season.

What gets misread

Willow catkins are a spring symbol and get blamed for a lot. It is worth being sceptical of a willow diagnosis made in late April without testing, because the same fortnight carries birch, poplar and ash, and birch alone dominates the air in this region.

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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