The pollen bulletin which runs until 27 March states that in the northern region the risk should be low to moderate, while in the Azores and Madeira the pollen concentration will remain at a low level.

According to the SPAIC forecast, spring will start with rain, which decreases the pollen load in the air, due to the "washing of the atmosphere" effect that is caused by precipitation.

These rains have been interspersed with some open with sun, which causes pollination to occur and that, on certain days or times, the concentration of pollen in the air can reach moderate to high levels, says the bulletin.

The pollen grains that are observed in the atmosphere are mostly from cypress, plane and pine trees and also from grassy herbs, sorrel and nettle, says SPAIC.

According to the association, the period from February to October is the one with the highest total concentrations of pollen, with peaks from April to July.

The pollen of herbs, trees and shrubs are usually the most important as inducers of allergic symptoms.