Birch pollen
The defining spring allergen of northern and central Europe, and one of the most potent: a single tree releases pollen in the hundreds of millions, and grains travel hundreds of kilometres on the wind. Its allergen cross-reacts with apple, cherry and hazelnut, which is why so many birch-allergic people also get an itchy mouth from raw fruit.
When it is in the air
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
Where it dominates
Strongest across Scandinavia, the Baltic states, Poland, Germany and the British Isles. Thins out around the Mediterranean, where birch does not grow well.
What the levels mean
| None | < 10 |
| Low | 10 – 49 |
| Moderate | 50 – 99 |
| High | 100 – 499 |
| Very high | ≥ 500 |
Concentrations in grains per cubic metre of air. These bands come from published clinical evidence but have not yet been checked against measurements for this species.