Research institute Nivel reports that GP visits for hay fever spiked last week. Around 142 out of every 100,000 people consulted a doctor for symptoms, up from 62 per 100,000 the previous week.

The numbers are notably higher than in past years. During the same week in 2025, 92 per 100,000 people saw a GP for hay fever, and in 2024, the figure was 89 per 100,000.

Hay fever sufferers are affected more during warm, dry, and sunny conditions due to higher pollen levels. Last Wednesday, much of the Netherlands experienced temperatures above 15 degrees Celsius, officially the first spring day of the year. Maastricht reached 19.3 degrees, setting a record for the warmest February 25 ever in the country.

Alder and hazel trees are responsible for most of the current hay fever symptoms. Being the first to bloom each year, their male flowers, or “catkins,” have been triggered early by the recent mild weather, spreading large quantities of pollen.

LUMC experts believe that a strong southern wind helped carry pollen from trees that bloomed earlier in Belgium and France into the Netherlands, contributing to the higher concentrations.

The hay fever season is beginning progressively earlier. Since 1977, hazel trees have been flowering about 40 days sooner on average, a shift attributed to climate change.

The surge in GP consultations overlaps with the tail end of the flu season. Physicians report that many patients confuse hay fever with a cold or mild flu, as both can cause tiredness and a congested feeling in the head.