Latin name: Corylus spp.
Plant description: Small, bushy tree with oval, serrated leaves. Pale yellow catkins produce the pollen. Fruit: hazelnut/filbert.
Distribution: UK: Countrywide. Also across much of Europe, North America and Asia and planted as an ornamental in more temperate regions.
Allergenicity and other health impacts: Hazel pollen has moderate to high allergenicity. It can cross-react with birch pollen so some birch-pollen sufferers may be affected by hazel pollen. There are only two allergenic pollen types that occur in the winter, hazel and alder, so if you have symptoms at that time then one or both of these may be the culprit.
Season: Mid-January to mid-April, usually peaking in February. The peak can start as early as December in very mild Winters or be delayed if the Winter weather is severe.