Fertiliser increases grass allergy

Spektrum der Wissenschaft

23.4.2025

Translation: machine translated

Meadows that are treated with nitrogen fertiliser not only produce significantly more pollen than unfertilised grassland. Their pollen also triggers stronger allergic reactions.

In spring in particular, farmers often treat their meadows with nitrogen fertiliser to stimulate the growth of grasses. However, this increases the allergy potential of the plants, as a Belgian research group reports in the specialist journal «The Lancet Planetary Health». This is because the plants then produce significantly more pollen, which also triggers stronger allergic reactions.

The experts led by Robin Daelemans from the Catholic University of Leuven compared pollen samples from 25 fertilised agricultural fields with those from the same number of unfertilised fields. They found that the former, at 3.6 milligrams of pollen per square metre, produced around six times as much pollen as the latter.

In addition, the team tested how strongly certain immune cells, which are part of the white blood cells, reacted to the pollen. To do this, the researchers took a blood sample from 20 volunteers with a diagnosed grass pollen allergy and carried out a so-called basophil activation test (BAT). This indicates the extent of an allergic reaction. The result: the pollen from the fertilised grassland activated the basophils around five times more strongly than that from the unfertilised meadows.

In recent decades, the number of people with hay fever has increased worldwide. According to experts, this is partly due to air pollutants that increase the allergy content of pollen. This study has now added another possible cause for the increase in pollen allergies. According to research, the amount of nitrogen in the environment has doubled in the last 100 years, mainly due to fertilisation.

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