Hazel (Tree)
Description
Hazel trees (Corylus species) are deciduous shrubs or small trees in the birch family (Betulaceae). They have rounded, doubly-serrated leaves and produce the edible hazelnuts (also called filberts) enclosed in leafy husks. Hazels are common in woodlands, hedgerows, and urban areas across Europe and parts of Asia. They produce distinctive yellow catkins in late winter that release abundant pollen before leaves emerge. Common species include common hazel (Corylus avellana) and Turkish hazel (Corylus colurna).
Allergy Symptoms
Hazel pollen causes:
- Sneezing and runny or congested nose
- Itchy, watery, red eyes
- Coughing and throat irritation
- Asthma flare-ups and wheezing
Hazel pollen contains the allergen Cor a 1, which is closely related to Bet v 1 in birch pollen — so if you’re allergic to birch, you’ll probably react to hazel too. Oral Allergy Syndrome (OAS) is common, causing mouth and throat itching from raw hazelnuts, apples, pears, cherries, peaches, and carrots. Cooking usually reduces the reaction.
Typical Pollination Period
Hazel trees are among the earliest to pollinate:
- UK and Western Europe: Can start as early as January, peaking February to March
- Central and Eastern Europe: Typically February to April
- Other regions: Generally late winter to early spring, depending on local climate
Geographic Distribution
Hazel trees grow widely in temperate regions:
- Europe: Common throughout, especially in woodlands and hedgerows
- Asia: Found in Turkey, the Caucasus, and extending into parts of China and Japan
- North America: American hazel (Corylus americana) is present but less common than in Europe
Tips for Allergy Sufferers
- Check pollen forecasts — hazel season starts earlier than most people realize
- Keep windows closed and use HEPA air purifiers
- Shower and change clothes after being outside
- Antihistamines or nasal corticosteroids can help — ask your doctor
- If you’re allergic to birch, expect to react to hazel too
- Watch for Oral Allergy Syndrome with hazelnuts and related foods
- For persistent symptoms, consider allergy testing or immunotherapy