Alder allergy

Alder allergy (Alnus) is an early spring allergen in Croatia. Alder flowers as early as February and March, making it the second-earliest tree (after hazel). It is cross-reactive with birch, hazel and hornbeam (all Betulaceae) - people allergic to birch usually react to alder as well. In continental Croatia, alder pollen concentrations can exceed 50 grains/m³ in February.

Symptoms of alder allergy are practically identical to those of birch - sneezing, a runny nose, watery eyes, an itchy palate and throat. In people with OAS, reactions to raw apple, pear and hazelnut also occur. Typically: symptoms start in February, ease in March, and then continue with birch in April.

The alder season in Croatia lasts from late January to mid-March, peaking in February. Warm winter days (above 8°C) speed up flowering. In Mediterranean Croatia the season starts in late January, while in continental Croatia it can last into early April in cold years.

Alder grows best along watercourses (rivers, streams, marshes), so it is widespread in Slavonia (along the Drava, Sava and Danube), the Posavina region, and along the wetland areas of Lika and Gorski Kotar. Mediterranean Croatia has less alder, but Istria and the northern Adriatic have noticeable concentrations. Velika Gorica, Sisak and Slavonski Brod are towns with traditionally high alder pollen concentrations.

Alder is cross-reactive with birch - if you are allergic to birch, start preventive treatment (antihistamines, nasal sprays) as early as January, before alder flowers. Immunotherapy for birch usually also covers alder (the PR-10 protein). On warm February days, avoid spending time along watercourses and damp, wooded areas.

Alder pollen cross-reacts with birch, hazel and hornbeam (the PR-10 protein), as well as with raw hazelnuts, apple, pear, peach, apricot, carrot, celery and kiwi. Heat treatment (cooking) breaks down the proteins, so cooked food usually does not trigger a reaction.

Other allergens