Pollen from trees and shrubs can trigger hayfever, a type of allergy – your doctor may call it seasonal allergic rhinitis.
Hayfever occurs when your body makes the mistake of treating the tree pollen, or pollen from shrubs, as a harmful organism, and the immune system goes into action by making antibodies to try to prevent it spreading. Symptoms of hayfever include sneezing, itchy, even watery, eyes and a stuffy nose.
About 1 in every 4 people in the UK who have hayfever are allergic to tree pollen.
Tree pollen allergy is seasonal, usually occurring mostly between February and June, when trees release pollen that can be carried in the wind – but not all tree pollens cause hayfever. Flowering trees such as apple and cherry trees have larger, sticky pollen that is normally carried by insects, so this doesn't tend to travel in the wind. Trees that have small, barely visible pollen are the culprits, especially those with catkins, and breathing in just a small amount of their pollen can trigger symptoms. The pollen can be carried by the wind for miles, so the tree releasing it won't necessarily be growing in your neighbourhood.
Pollen counts – the amount of pollen in the air – can vary. Symptoms normally appear when the count is above 50. Weather and biological factors can have an effect, so the pollen counts – and your symptoms – can be worse in some years than others. Pollen counts are often higher on warmer dry days than cooler wet days as rain removes pollen from the air, and they won't be the same in every region, so where you live in the country can determine your allergy symptoms. You may also have symptoms to only one type of tree pollen or to several, so when you experience symptoms will depend on which tree pollen you are allergic to and when it is released.
According to the Met Office, on average, the following trees release pollen during these months:
Alder (Alnus) – pollen released between January and late April, peaking between mid-February and early April
Ash (Fraxinus) – pollen released between early March and late May, peaking between early April and early May
Birch (Betula) – pollen released between early March and mid-June, peaking between late March and mid-May
Elm (Ulmus) – pollen released between early February and late April, peaking between early March and early April
Hazel (Corylus) – pollen released between early January and late April, peaking between mid-February and mid-March
Lime (Tilia) – pollen released between early June and early August, peaking between mid-June and mid-July
Oak (Quercus) – pollen released between late March and mid-June, peaking between late April and early June
Pine (Pinus) – pollen released between early April and late July, peaking between early May and late June
Plane (Plantanus) – pollen released between early March and late May, peaking between mid-April and mid-May
Poplar (Populus) – pollen released between mid-March and early May, peaking between mid-March and early April
Yew (Taxus) – pollen released between early January and late April, peaking between late February and late March
Willow (Salix) – pollen released between early February and early May, peaking between early March and early April
Other trees and shrubs that release allergy-triggering pollen include beech, juniper, sweet chestnut and walnut.
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