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Pollen seasons and cross-reactive foods

The Nordic and Baltic pollen calendar: 16 pollen and spore sources with their season, peak and food cross-reactions, plus the 14 substances EU law makes declarable on a food label.

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.

The pollen calendar

One row per airborne allergen source, one column per month, for the mainland Baltic states and southern Finland. This is a phenology calendar, not a measurement: it says when a plant flowers here in a normal year, not how much pollen is in the air today. Denmark and southern Sweden run roughly two to three weeks ahead of this grid; northern Finland, Sweden and Norway roughly three to four weeks behind; and every season moves with the spring.

● peak weeks · ○ usually airborne · blank: out of season. Windows are the typical mainland pattern published year after year by the national aerobiology monitoring programmes of the region · checked 2026-09-06

Month by month

The same calendar read the other way round, for when the question is "what is doing this to me right now".

November, December and January are the quiet months outdoors in this region. Symptoms that persist through them are usually indoor ones — house dust mite, pets, indoor mould in a damp building — and those follow a different logic from a calendar: worse indoors, worse on waking, unchanged by rain.

What each pollen cross-reacts with

Pollen-food cross-reactions happen because plant proteins repeat across species. An immune system trained on birch pollen meets an almost identical protein in an apple and reacts to it. The result is usually confined to the mouth and throat, and usually disappears when the food is cooked — with exceptions that are set out on the oral allergy syndrome page.

Potency here means how strong an allergen the pollen is, not how much of it is in the air. The two come apart badly: nettle and conifer pollen are among the most abundant particles of the northern summer and among the weakest allergens, while birch and grass dominate the clinic.

The fourteen allergens an EU label must declare

Annex II of Regulation (EU) No 1169/2011 lists fourteen substances that must be declared whenever they are used in a food sold in the EU and are still present in the finished product. The list is closed, it mixes true allergies with coeliac disease and with a preservative intolerance, and it says nothing about severity. Each entry below has its own page: what the reaction actually is, where the substance hides, which narrow exemptions apply, and what it cross-reacts with.

Source: Regulation (EU) No 1169/2011 on the provision of food information to consumers, Annex II · checked 2026-09-06

Two things worth reading first

The live forecast, and what this page is not

A forecast and a calendar answer different questions. The forecast answers "is it bad today"; this page answers "what is it, when does it happen, and what else does it touch".

The European forecast that most pollen apps and feeds are built on — the CAMS European air quality service, republished through the free Open-Meteo API — models six species: alder, birch, grass, mugwort, ragweed and olive. Five of those are relevant here, and olive is a Mediterranean tree that plays no part in the northern season. Everything else on the calendar above has a season and no forecast: hazel, willow, poplar, ash, oak, conifers, sorrel, rye, plantain and nettle, plus the outdoor mould spores that dominate late summer.

That gap matters when a forecast reads low and you feel terrible. In late August a clear grass and birch forecast tells you very little, because the things actually in the air are mugwort, plantain and Alternaria spores, and only one of those three is modelled at all.

Source: Open-Meteo, which republishes the CAMS European air quality pollen forecast · checked 2026-09-06

How this page was built

Season windows are the typical mainland pattern for Estonia, Latvia, Lithuania and southern Finland as published year after year by the national aerobiology monitoring programmes: the Estonian Environment Agency, the University of Turku Aerobiology Unit, the Palynological Laboratory of the Swedish Museum of Natural History, Astma-Allergi Danmark and the Norwegian Asthma and Allergy Association. Deliberately, no grain count, concentration or percentage appears anywhere on this surface — those are measurements taken on a particular day at a particular trap, and reprinting one as a general fact would be a fabrication.

Allergen molecule names — Bet v 1, Phl p 5, Art v 1, Ara h 2 — follow the official WHO/IUIS Allergen Nomenclature list. The legal content comes from the consolidated text of the Regulation itself. The cross-reaction syndromes are the long-established clinical patterns described in the allergy literature, paraphrased rather than quoted.

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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