Ragweed pollen
An invasive North American weed that has spread through the Pannonian basin and the Balkans, with a second front in the Rhône valley. It is the most potent pollen on this list — symptoms begin at single-figure counts — and its season runs late, filling the gap between summer grass and the first frost.
When it is in the air
- Jan
- Feb
- Mar
- Apr
- May
- Jun
- Jul
- Aug
- Sep
- Oct
- Nov
- Dec
Where it dominates
Hungary, Croatia, Serbia, Romania and northern Italy above all, and the Rhône-Alpes region of France. Spreading northwards.
What the levels mean
| None | < 3 |
| Low | 3 – 9 |
| Moderate | 10 – 49 |
| High | 50 – 199 |
| Very high | ≥ 200 |
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.