Allergy to Betulaceae
Allergy to Betulaceae is one of the most common forms of hay fever in northern Europe and in the Italian Alpine and pre-Alpine regions. It is characterised by an early pollen season, which sometimes precedes spring, and by frequent allergic reactions to related foods (due to cross-reactions) which can affect the patient’s dietary habits. Like other forms of hay fever, it can be effectively managed with an integrated approach comprising drug therapy and, where indicated, allergen-specific immunotherapy (AIT).
What is a Betulaceae allergy?
The Betulaceae are a botanical family comprising trees widespread in the temperate regions of Northern Europe and, in Italy, in mountainous, pre-Alpine and northern areas. The species of greatest allergological significance belong to the genera Betula (birch), Alnus (alder), Corylus (hazel) and Carpinus (hornbeam).
The clinically most important species is Betula verrucosa (common birch), whose pollen is considered one of the most potent pollen allergens, capable of inducing sensitisation even at considerable distances from pollination sites, thanks to its lightness and ease of airborne dispersal.
Although birch is typically associated with Northern European climates, it is also found in significant numbers in the northern regions of Italy, where it is a major cause of early-season allergic rhinitis.
[Biedermann T, Winther L, Till SJ, Panzner P, Knulst A, Valovirta E. Birch pollen allergy in Europe. Allergy. 2019 Jul;74(7):1237-1248.]
The main allergen: Bet v 1
The main allergen in birch pollen is Bet v 1, which accounts for over 90 per cent of IgE-specific reactivity in patients allergic to birch pollen, making it the dominant molecular marker for both diagnosis and the assessment of suitability for allergen-specific immunotherapy.
The clinical significance of Bet v 1 extends beyond a simple reaction to pollen: structurally homologous proteins present in numerous plant-based foods underpin the cross-reactivity between birch and food, a distinctive and characteristic feature of this form of pollinosis compared with others.
[Breiteneder H, Kraft D. The History and Science of the Major Birch Pollen Allergen Bet v 1. Biomolecules. 2023 Jul 19;13(7):1151.
Kleine-Tebbe et al. Bet v 1 and its Homologs: Triggers of Tree-Pollen Allergy and Birch Pollen-Associated Cross-Reactions. Molecular Allergy Diagnostics (pp.21-42)]
Pollen season: when symptoms appear
Allergy to Betulaceae is defined as a pre-spring pollinosis: flowering occurs well before the spring season, with symptoms appearing as early as the final weeks of winter.
- Alder and hazel: the first to flower, as early as January–February in milder areas
- Birch: main flowering period between March and May, with pollen peaks varying according to altitude and weather conditions
- Hornbeam: later flowering, lasting until May–June
The overlap in the flowering seasons of the various species within the Betulaceae family, combined with cross-reactivity between their allergens, often results in a longer overall symptomatic period than would be expected for any single species considered in isolation. Annual climatic variations can bring forward or delay the start of the pollen season by as much as several weeks.
[Ariano R. & Bonifazi F. Aerobiologia ed allergeni stagionali. Editore ECIG, 2006
[G D'Amato et al. Allergenic pollen and pollen allergy in Europe. Allergy. 2007 Sep;62(9):976-90]
Symptoms of Betulaceae allergy
Symptoms appear during the pollination season and may affect the upper respiratory tract, the eyes and, in susceptible individuals, the lower respiratory tract. Birch pollen is highly allergenic: symptoms can be severe even in the early stages of the season, when pollen concentrations are still relatively low.
Nasal symptoms
- Repeated sneezing
- Intense nasal itching
- Profuse watery nasal discharge
- Nasal congestion
Bousquet J, et al; Aria Workshop Group; World Health organization. Allergic rhinitis and its effect on asthma. J Allergy Clin Immunol 2001; 108: S147–S334.
Global Initiative for Asthma. Global Strategy for Asthma Management and Prevention, 2025. Updated 15 November 2025. Available from: www.ginasthma.org.
Eye symptoms
- Redness of the eyes
- Itchy and burning eyes
- Excessive tearing
Bousquet J, et al; Aria Workshop Group; World Health organization. Allergic rhinitis and its effect on asthma. J Allergy Clin Immunol 2001; 108: S147–S334.
Global Initiative for Asthma. Global Strategy for Asthma Management and Prevention, 2025. Updated 15 November 2025. Available from: www.ginasthma.org.
Bronchial symptoms
- Dry cough
- Wheezing
- Dyspnoea (shortness of breath)
- Chest tightness
Bousquet J, et al; Aria Workshop Group; World Health organization. Allergic rhinitis and its effect on asthma. J Allergy Clin Immunol 2001; 108: S147–S334.
Global Initiative for Asthma. Global Strategy for Asthma Management and Prevention, 2025. Updated 15 November 2025. Available from: www.ginasthma.org.
Oral allergy syndrome (OAS)
A characteristic and distinctive feature of birch allergy is its frequent association with oral allergy syndrome (OAS): itching, tingling and swelling localised in the mouth, on the lips and on the tongue, which typically appear within a few minutes of ingesting specific raw plant-based foods. The symptoms are generally mild, self-limiting and resolve spontaneously, but their onset can significantly affect the patient’s eating habits. In rare cases, following the consumption of significant quantities of such foods, or in the event of impaired gastric acidity, food allergy symptoms may be more debilitating and systemic in nature.
[Asero R. et al. Oral allergy syndrome: an update for the clinician. Eur Ann Allergy Clin Immunol, 2013.]
Cross-reactivity between birch and foods
Cross-reactivity between birch pollen and certain plant-based foods is one of the most characteristic features of this pollen allergy and stems from the structural homology between Bet v 1 and the PR-10 proteins found in numerous foods.
The foods most frequently involved (non-exhaustive list) are:
- Fruit: apple, peach, apricot, cherry, plum, strawberry, raspberry, pear, kiwi.
- Nuts and pulses: hazelnuts, almonds, walnuts, pistachios, peanuts, peanuts.
- Vegetables: carrot, celery, fennel, parsley, tomato.
The most common and clinically significant association is that between apples and hazelnuts, which share PR-10 proteins most similar to Bet v 1. However, certain minor allergens and panallergens are also responsible, albeit less frequently, for cross-reactions between birch and plant-based foods.It is important to emphasise that cross-reactivity does not necessarily lead to clinical symptoms in all sensitised individuals: clinical significance must be assessed on a case-by-case basis by an allergy specialist.
[Yukinori Kato, Taiyo Morikawa, Shigeharu Fujieda. Comprehensive review of pollen-food allergy syndrome: Pathogenesis, epidemiology, and treatment approaches. Allergol Int. 2025 Jan;74(1):42-50
Ciprandi G, Comite P, Mussap M, De Amici M, Quaglini S, Barocci F, Marseglia GL, Scala E.
Profiles of Birch Sensitization (Bet v 1, Bet v 2, and Bet v 4) and Oral Allergy Syndrome Across Italy. J Investig Allergol Clin Immunol. 2016;26(4):244-8.
Popescu FD. Cross-reactivity between aeroallergens and food allergens. World J Methodol. 2015;5(2):31-50.]
Impact on quality of life
Allergy to Betulaceae can have a significant impact on the quality of life of those affected, both due to respiratory symptoms and the dietary implications associated with cross-reactivity.
The most significant consequences for the patient include:
- Severe respiratory and ocular symptoms during the early pollen season
- Sleep disturbances caused by symptoms during peak pollen weeks
- Reduced ability to concentrate and impaired performance at work or school
- Restrictions on dietary habits to avoid cross-reactive foods
- Worsening of asthma in patients with bronchial comorbidities
- Psychological impact associated with managing dietary restrictions
Early pollen season, which brings spring forward to a time when patients may be less prepared, can amplify the clinical impact and require treatment planning to be in place before the season begins.
Laurent Laforest, Jean Bousquet, Guilhem Pietri, Vasilisa Sazonov Kocevar, Donald Yin, Yves Pacheco, Eric Van Ganse. Quality of life during pollen season in patients with seasonal allergic rhinitis with or without asthma. Int Arch Allergy Immunol. 2005 Mar;136(3):281-6]
Exposure reduction: practical measures
As with other types of hay fever, reducing exposure to birch pollen is difficult but possible through targeted behaviour. Exposure-reduction measures complement drug therapy and do not replace it.
- Monitor regional pollen forecasts and limit time spent outdoors on days when pollen concentrations are high
- Avoid outdoor activities during the middle of the day and on windy, dry days, when pollen dispersal is at its highest
- Keep windows closed during pollen peaks and use air conditioning fitted with suitable filters
- Take a shower and change your clothes after being outdoors
- Wear wraparound sunglasses to reduce contact between pollen and the mucous membranes of the eyes
- Avoid being near birch trees and areas with a high concentration of birch trees during the flowering season
These exposure-reduction measures are provided for information purposes and should be regarded as complementary to drug therapy and any immunotherapy, as part of a treatment plan agreed with your doctor.
Hogaard Respiratory Medicine 2025
GINA 2025;
Bousquet ARIA JACI 2001
Frequently Asked Questions
Birch and hazel belong to the same botanical family (Betulaceae) and share structurally similar allergens. For this reason, people who are sensitised to birch may also react to hazel pollen, and vice versa. However, some patients react only to hazel pollen. The hazel tree flowers before the birch (from January to February), so for patients who are hypersensitive to the Betulaceae family, the allergy season can begin as early as the middle of winter.
Certain proteins found in raw apples and unroasted hazelnuts are structurally very similar to the main birch allergen, Bet v 1. The immune system of people allergic to birch recognises them as similar and reacts in the same way, causing the symptoms of oral allergy syndrome. Generally, cooking or industrial food processing denatures these proteins, eliminating or reducing cross-reactivity.
Oral allergy syndrome caused by cross-reactivity with birch is generally a mild, localised reaction confined to the mouth, which resolves spontaneously within a few minutes. However, in a small number of cases, the reaction may spread beyond the mouth. For this reason, any reaction to a food should be assessed by an allergy specialist, who will be able to determine the individual’s risk profile.
Yes. In the absence of appropriate treatment, allergic rhinitis caused by birch pollen can progress to involve the lower airways (bronchial asthma), in accordance with the phenomenon known as the ‘allergic march’. Cross-reactive food reactions also tend to appear or become more widespread over time, as sensitisation becomes established. Early diagnosis and an active treatment plan are essential to limit this progression.
Yes. Allergen-specific immunotherapy (ASIT) using birch extracts is the only treatment capable of modifying the patient’s immune response, reducing sensitisation and the long-term progression of the disease. Suitability for immunotherapy must be assessed by an allergy specialist.
ref. Roberts. EAACI guidelines. Allergy 2018)
You should see a doctor if you experience nasal, eye or bronchial symptoms that occur regularly in late winter or spring, or if you have oral reactions after eating apples, hazelnuts, or raw fruit and vegetables. An allergy assessment using skin prick tests can confirm the diagnosis, determine your sensitisation profile and establish the most appropriate treatment plan.
Practical insights
Nota informativa
The information on this page is for educational purposes only and is not a substitute for the advice of a doctor or other qualified healthcare professionals. For a clinical assessment and any treatment decisions, including the choice and management of drug therapies and allergen-specific immunotherapy, you should consult your specialist doctor. The practical guidelines provided are intended as complementary measures to support exposure management, as part of an individualised treatment plan.