Pollen

Microscopic grains produced by plants in order to reproduce. Each plant has a pollinating period. These can vary depending on the plant, climate and region. See also the tree , weed and grass pollen pages for more information on the main pollens involved in allergic reactions.

Pollen Allergy

A hypersensitive reaction to pollen. While grass pollens are generally the most common cause of hay fever (seasonal allergic rhinitis), other pollen types are also important. These include tree pollens such as alder , hazel , birch , beech , cypress , pine , chestnut and poplar , and weed pollens such as plantain , mugwort and ragweed . The relative importance of the kinds of pollen that can cause hay fever varies between different climatic and vegetation zones. For example, ragweed pollen, although very common in North America, is present in Europe only in the French Rhône valley and some areas of Eastern Europe, while the pollen most associated with seasonal allergy in Mediterranean regions is the olive tree. A person allergic to one pollen is generally also allergic to members of the same group or family (e.g. Betulaceae ).
Pollen induced reactions include extrinsic asthma , rhinitis and bronchitis .