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Alder pollen

Alder (Alnus glutinosa, Alnus incana) is airborne here from february to april, peaking late March to mid-April. 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

Two alders matter here. Black alder holds the wet ground — river banks, ditches, fen woodland — and grey alder colonises abandoned farmland, which is why it has spread so widely across Estonia, Latvia and Finland over the last century. Both are wind-pollinated and both flower on bare wood, so a stand of alder along a stream is a pollen source in plain sight.

When it is in the air

Alder overlaps hazel and hands over to birch. In the Baltic and southern Finland the window is February to April with the strongest days between late March and mid-April; further south, in Denmark and southern Sweden, it starts weeks earlier. Grey alder tends to flower slightly ahead of black alder, which stretches the season at both ends in regions where both grow.

What it feels like

Alder produces classic upper-airway hay fever: blocked and running nose, itchy palate, red gritty eyes. Because it arrives in early spring, it is common for people to attribute a whole month of symptoms to a persistent virus and only recognise the pattern when it repeats the following year at the same time.

What it cross-reacts with

Alder is a Fagales tree and Aln g 1 is a Bet v 1 homologue, so alder allergy travels with hazel, birch and oak almost as a single sensitivity. Most people are found to be sensitised to the group rather than to one member of it, and the birch food list applies. Clinically it is usually the birch season that gets the credit, because it is louder — but for someone whose symptoms begin in March, alder is the trigger and birch is still weeks away.

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

Foods reported to cross-react:

ApplePearCherryPlumHazelnutCarrotCelery

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: Aln g 1 (PR-10, a Bet v 1 homologue). These are the official WHO/IUIS names, and they are what a component-resolved blood test reports.

What actually helps

Alder is one of the five pollen types the CAMS European forecast — the data behind the Open-Meteo pollen feed — actually models, so a forecast number exists for it. Use it the way a rain forecast is used: to decide whether to open a bedroom window overnight or hang washing outdoors, not to decide whether you have an allergy.

What gets misread

A common assumption is that alder in a garden is the problem and cutting it solves it. Wind-pollinated tree pollen travels tens of kilometres and is measured hundreds of kilometres from source; removing one tree changes very little. What does change things is keeping it out of the bedroom — closed windows on windy dry afternoons, and hair washed before the pillow.

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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