Spring in continental Croatia is not just a season of grass pollen — from February to May the air is filled with tree allergens. Although tree flowering occurs mainly before the tourist season, many allergy sufferers experience very severe symptoms precisely during this period.

Most important tree allergens

Birch (Betula)

The strongest European tree allergen. A single tree produces enormous quantities of pollen, which wind can carry several hundred kilometers.

  • season: mid-March to end of April or mid-May, depending on year
  • peak: first half of April
  • regions: entire Croatia, strongest in northwestern part
  • birch allergen causes virtually all allergic symptoms

Many birch allergy sufferers simultaneously react to multiple other tree allergens due to cross-reactivity within the Betulaceae family.

Alder (Alnus) and Hazel (Corylus)

  • season: January to March
  • earliest pollen allergens — already in winter
  • in warmer winters, peak can be as early as end of January
  • symptoms are often mistaken for colds because they are unexpected in winter

Oak (Quercus)

  • season: April to May
  • produces large quantities of pollen, but allergens are weaker than birch
  • significant in continental Croatia, especially in Slavonia and Posavina

Beech (Fagus)

  • season: May
  • significant in continental Croatia
  • beech does not flower equally every year — cyclic "mast years" with large waves every 3–5 years

Ash (Fraxinus) and Poplar (Populus)

  • season: March to April
  • ash can be an almost equally strong allergen as birch
  • poplar's cottony seeds are not allergenic, but often mix with pollen from other trees

Olive (Olea europaea) — coast

  • season: end of May to June
  • relevant in Dalmatia and Istria
  • does not flower equally every year

Food cross-reactions (birch-fruit syndrome)

Birch is known for the most extensive food cross-reactivity of all allergens. If you are allergic to birch, you will likely experience symptoms after eating:

  • apple, pear, peach, apricot, plum, cherry, sour cherry — most common
  • almonds, hazelnuts, walnuts, peanuts
  • kiwi, carrot, celery, tomato
  • raw potato

Symptoms are called oral allergy syndrome:

  • itching in the mouth, tingling
  • mild swelling of lips or tongue
  • red ridges on the throat
  • very rarely — systemic reactions

Cooked or baked food usually does not cause symptoms because heat breaks down allergenic proteins. Canned fruit, jams and compotes are usually well tolerated.

Symptoms of tree allergen allergy

Classic symptoms of allergic rhinitis:

  • watery discharge from nose
  • sneezing in fits in the morning
  • nasal congestion
  • red and itchy eyes
  • itching of palate and throat
  • increased cough in patients with asthma

Strong symptoms during March and April, especially with oral syndrome after eating apple or peach, are a strong clinical indicator of birch allergy.

What helps

Approach is similar to other pollen allergies:

  • Second-generation antihistamines throughout the season
  • Nasal corticosteroid spray started 5–10 days before season — for birch this means end of February in continental Croatia
  • Eye drops for watering
  • Avoid drying laundry outside during peak season
  • Sunglasses reduce the amount of pollen entering eyes
  • During severe symptoms, plan a shorter stay at the coast — birch season on the coast is shorter and less pronounced

Immunotherapy for birch

Specific immunotherapy for birch pollen is available in sublingual (tablets under the tongue) and subcutaneous form. Treatment lasts 3–5 years and has proven effective in reducing symptoms and medication needs, as well as providing long-term protection against further allergy development.

Practical recommendations for the season

  • Do not plan garden work for April if you are allergic to birch.
  • Ventilate apartment in the morning before 9 or late in the evening.
  • Car pollen filter is worthwhile using.
  • Shower before bed and fresh bedding reduce nighttime exposure.
  • Check pollen forecast and adjust outdoor activities to days with lower concentrations.

Note

This is not medical advice. For individual therapy advice and especially about immunotherapy, consult your family physician or allergist.