Alder pollen
The first pollen of the year, often airborne in January while everything else is still dormant. It belongs to the same family as birch and shares its allergens closely enough that most people allergic to one react to the other, which effectively extends the birch season backwards by two months.
When it is in the air
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
Where it dominates
Much the same range as birch, with the highest counts in central Europe and around waterways, where alder grows.
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.