Pollen is suspended in the air on hot and sunny days. When it is windy, they can be carried for miles! The pollen rate in the atmosphere is lowest on rainy days or when it is cold and damp.

There are 3 categories of pollen:

Tree pollen:

There are six main families of tree which cause allergic reactions. A distinction is drawn between trees without catkins which are mostly present in Mediterranean regions (cypress, plane, olive) and trees with catkins tolerating all kinds of climate (oak, ash, birch, hornbeam, alder, hazelnut).
Pollination extends over a lengthy period running from March to September and is highly variable depending on the species.



This can be found in gardens, forests, water and on lawns and rocks. Just a small concentration of grass pollen is enough to trigger an allergy. Grass pollen represents a botanical family of some 12,000 species!

A distinction is made between:
o Fodder grasses: cocksfoot, timothy, vernal, ryegrass, meadow grass, etc.
o Cereal grasses: oat, wheat, corn, barley, rye, etc.

The period of pollination runs from May to September with peaks in May, June and July.


Herbaceous grasses have soft and supple stems and leaves. They are present in cities and along roads and tracks. 
The smaller and lighter the grains, the longer they remain in the atmosphere and the further they travel.
The most allergenic herbaceous grasses are ragweed and mugwort.
Aromatic plants such as citronella grass, absinth and tarragon are part of the same asteracea family comprising some 50,000 species.

The pollen season for herbaceous grass runs from March to September but peaks between July and September.

Stallergenes Greer UK