KU Leuven: Even during pollen season, contact with nature can be beneficial for people with birch pollen allergies

During the pollen season, many allergy sufferers tend to avoid nature. This is not entirely correct, according to research by KU Leuven into biodiversity and health. People with birch pollen allergy experience fewer symptoms after exposure to certain natural environments such as grasslands and forests. An important condition is that the environment is not dominated by allergenic tree species and that there is no large concentration of pollen and air pollution.

With the pleasant spring temperatures, many people seek out the outdoors and nature. Because of the corona virus, social life also largely takes place outside. This poses a dilemma for people with a pollen allergy: go to nature and therefore also confront the dreaded pollen or stay indoors? In the RespirIT project, researchers from KU Leuven, in collaboration with UHasselt, UNamur, Sciensano and the RMI, searched for the answer.

Via a smartphone application, the researchers registered the movements of 144 Belgian adults with a birch pollen allergy. The participants were followed during the birch pollen season (January-May) of 2017 and 2018. Each evening they also indicated via the app which allergy symptoms they had experienced that day.
Exposure to nature
“We analyzed which environment the participants were exposed to and then looked at which days did or did not cause severe allergy symptoms,” says Michiel Stas, who completed his PhD at KU Leuven within the RespirIT project. “We saw that severe symptoms were linked to high pollen concentrations and strong air pollution. These complaints could also occur one or two days after exposure. Rather surprisingly, we also found that the participants developed no or only mild symptoms after exposure to grasslands and forests.

“We can therefore say that people with a birch pollen allergy should not necessarily avoid nature during the pollen season. An important condition is that the environment they come into contact with is not dominated by allergenic tree species such as alder, hazel and birch. ”

Bad air quality, more severe symptoms
The research shows that not only allergenic tree species and pollen are an important source of allergy complaints, air quality is also a crucial factor. “Air pollution affects the respiratory system, making people more sensitive to pollen,” adds promoter Ben Somers (Department of Forest, Nature and Landscape, KU Leuven). “Under the influence of air pollution, the trees also produce pollen that contains more allergens and can therefore trigger more severe allergic reactions.”

“More nature and greener cities can contribute to improving the living environment. In addition, it is important that nature is diverse and that allergenic tree species do not predominate, so that people with a pollen allergy can also enjoy these beneficial effects ”, Michiel Stas concludes. “Anyone with a birch pollen allergy should certainly not lock themselves up during the pollen season, but choose the place and time for a refreshing walk strategically. The weather forecast or the Sciensano website can help you with that. ”