The dry and sunny spring weather causes the pollen levels to rise. The heat causes the trees to develop and pollen to release from their pendants.
Warm and dry air also means that pollen spreads across larger areas, says Åslög Dahl, biologist and responsible for the pollen lab at the University of Gothenburg.
Hassel and Gråal have bloomed since January and now it is Gråal and Klibbal that is in turn. The next few days there is a high risk of high levels of alpollen in Götaland, Svealand and the southern parts of Norrland, according to The pollen report which is run by the Natural History Museum.
Many birch pollen allergies also react to al and hazel. When the birch comes then, it is likely to be worse than usual, so it is high time for those who need to start medication now.
Birch pollen has a natural oscillation that usually goes in two -year cycles and last year it was very sparse in large parts of Sweden. So the expectation is that it will be over funds this year, says Åslög Dahl.
Since birch pollen travels easily with winds, the allergies can feel it long after flowering is over locally.
Depending on how the air currents go, pollen can come here both from northern Finland but also further south and from Ukraine.
Soon, the Salg Pollen that some birch pollen allergies may also react to.
But it is not spread as far as birch, says Åslög Dahl