More than 20 percent of children and over 30 percent of adults develop at least one allergic disease over the course of their lives. Birch causes symptoms for most hay fever sufferers, followed by the early bloomers hazel and alder.
Trees normally release more pollen in the morning and midday. The amount and concentration of pollen and allergenic substances can vary greatly and depend on various factors such as temperature, weather, wind and air pollutants. Nitrogen oxides and ozone can increase the amount of pollen and increase their effects. It is practically impossible to completely protect yourself from pollen, as it can get into your own four walls through the wind, clothing and hair. However, there are useful tips and tricks to best reduce symptoms during the pollen season. The German Allergy and Asthma Association (DAAB) says that the symptoms of those affected can be most severe during the morning or evening hours. Outside cities, rooms should therefore be ventilated in the evening and within the city in the early morning.