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Birch pollen

Birch (Betula pendula, Betula pubescens) is airborne here from april to june, peaking late April to mid-May in the Baltic, the first half of May in southern Finland, and late May to early June in Lapland. Allergenic potency: high. Cross-reacts with apple, pear, cherry, plum and others.

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

Birch is the defining tree of this region and the single most important outdoor allergen in it. Silver birch and downy birch together cover a large share of the forest area of Estonia, Latvia, Lithuania, Finland and Sweden, they colonise every clearing and roadside, and they are planted in gardens and along streets in every town. There is no realistic way to avoid the source.

When it is in the air

The birch season is short, violent and highly variable between years. In the Baltic states the heaviest days usually fall between the last week of April and mid-May; southern Finland runs a week or so later; Lapland can be four weeks later still. The tree also masts, so a heavy flowering year is often followed by a lighter one, and a single warm, dry, windy week can compress most of the season into a few days.

What it feels like

Eyes are usually the worst of it: swollen, streaming, gritty, worse in wind. Add a blocked nose, sneezing, an itchy palate and, for many people, genuine exhaustion — the constant low-grade inflammation and broken sleep of a bad May is not imagined. Asthma symptoms commonly step up during the peak fortnight.

What it cross-reacts with

Bet v 1 is the reason birch matters far beyond hay fever. It is a PR-10 protein, and near-identical proteins occur in apple (Mal d 1), stone fruit, hazelnut (Cor a 1), carrot (Dau c 1), celery (Api g 1), soy (Gly m 4) and peanut (Ara h 8). An immune system trained on birch pollen recognises them, and biting into a raw apple in May produces an itchy mouth. This is pollen-food allergy syndrome, and in birch country it is the most common food allergy in adults.

Related pollens: alder, hazel, oak, hornbeam and beech.

Foods reported to cross-react:

ApplePearCherryPlumPeachApricotHazelnutAlmondCarrotCeleryParsnipSoy drink and tofuPeanutKiwi

A cross-reaction is not the same as a food allergy that started with food, and the difference decides how serious it is. Read how oral allergy syndrome works before drawing conclusions from this list, and note that several of these foods also appear on the fourteen declarable EU allergens for entirely separate reasons.

Named allergen molecules: Bet v 1 (PR-10, the major allergen), Bet v 2 (profilin), Bet v 6. These are the official WHO/IUIS names, and they are what a component-resolved blood test reports.

What actually helps

Birch pollen is one of the five types the CAMS European model forecasts, so a daily number exists. Preventive treatment works better than rescue treatment: nasal steroid sprays need days to reach full effect, so they are started before the season, not during it. Birch is also the classic candidate for allergen immunotherapy, which is a clinician-led, multi-year decision — not something to start from a web page.

What gets misread

Two things get confused every year. First, a raw apple causing an itchy mouth in May is birch, not "an apple allergy" — the same apple baked in a pie is usually fine, because Bet v 1 homologues fall apart with heat. Second, the peak is not the whole season: the tail in late May still carries enough pollen to keep symptoms going after the visible catkins have gone.

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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