Immunotherapy for tree pollen allergy offers a fundamentally different approach to managing hay fever compared with over-the-counter (OTC) medications. Tree pollen allergy affects a significant proportion of the UK population, with birch, alder, hazel, and ash among the most common triggers between January and May. Whilst antihistamines and intranasal corticosteroids provide effective day-to-day symptom relief, they do not address the underlying immune response. Allergen immunotherapy, available as injections or sublingual tablets, aims to desensitise the immune system over time — potentially offering lasting benefit well beyond the treatment period. This article compares both approaches to help patients and clinicians make informed decisions.

Understanding Tree Pollen Allergy and Its Impact in the UK

Tree pollen allergy, commonly known as hay fever or allergic rhinitis, affects a significant proportion of the UK population. The NHS estimates that hay fever affects approximately 1 in 5 people in the UK at some point in their lives, and tree pollen allergy accounts for a notable proportion of these cases. Unlike grass pollen, which peaks in summer, tree pollen season typically runs from late January through to May, with birch, alder, hazel, and ash being among the most common triggers. Birch pollen is a major and common cause of tree pollen allergy in the UK, with its season generally peaking between April and May.

Importantly, birch, alder, and hazel belong to the same botanical homologous group, meaning their pollen proteins are closely related. Individuals sensitised to birch are therefore often also reactive to alder and hazel — a cross-reactivity that is clinically relevant both for diagnosis and for the selection of allergen extracts used in immunotherapy.

Symptoms can range from mild to severely debilitating and typically include:

• Persistent sneezing and nasal congestion

• Itchy, watery, or red eyes (allergic conjunctivitis)

• Itchy throat, ears, or roof of the mouth

• Fatigue and difficulty concentrating — sometimes referred to as 'brain fog'

For many individuals, these symptoms significantly impair quality of life, affecting sleep, work performance, and daily activities. In those with co-existing asthma, tree pollen exposure can also trigger or worsen respiratory symptoms, making effective management particularly important. Understanding the distinction between tree and grass pollen allergy is clinically relevant, as it influences both the timing of symptoms and the specific allergen extracts used in immunotherapy.

Sources: NHS hay fever (allergic rhinitis) page; BSACI Rhinitis guideline; Met Office UK pollen calendar.

How Immunotherapy Works for Tree Pollen Allergy

Allergen immunotherapy (AIT) is the only treatment currently available that modifies the underlying immune response to allergens, rather than simply suppressing symptoms. It works by gradually desensitising the immune system through repeated, controlled exposure to increasing doses of the specific allergen — in this case, tree pollen extract, most commonly birch.

There are two main delivery routes used in the UK:

• Subcutaneous immunotherapy (SCIT): Allergen extracts are administered via injections, typically in a hospital or specialist clinic setting, due to the small risk of systemic allergic reactions.

• Sublingual immunotherapy (SLIT): Allergen extracts are delivered as drops or dissolvable tablets placed under the tongue. A UK-licensed birch pollen SLIT tablet (ITULAZAX 12 SQ-Bet) is available for adults with moderate-to-severe birch pollen-induced allergic rhinoconjunctivitis. Because birch, alder, and hazel belong to the same homologous group, this product also provides coverage for cross-reactive tree pollen allergens. Per the Summary of Product Characteristics (SmPC), treatment should ideally be initiated approximately 16 weeks before the start of the birch pollen season and continued throughout the season. The first dose must be administered under medical supervision; subsequent doses may be self-administered at home.

The mechanism involves shifting the immune response away from the allergic (Th2-mediated) pathway towards a more tolerant (Th1 and regulatory T-cell) response. Over time, this reduces the production of IgE antibodies responsible for triggering allergic symptoms and promotes the release of blocking antibodies (IgG4). A standard course of immunotherapy typically lasts three to five years, and the benefits can persist for several years after treatment is completed — a key advantage over conventional medications.

Key contraindications and precautions: AIT should not be initiated in patients with uncontrolled or severe asthma (FEV₁ persistently below 70% predicted despite treatment). Other contraindications include active or uncontrolled autoimmune disease, malignancy, and severe cardiovascular conditions. AIT is not routinely initiated during pregnancy, though it may be continued under specialist supervision in those already established on treatment. Active oral inflammation (e.g., oral ulcers, recent dental surgery) is a precaution for SLIT. Patients and prescribers should consult the relevant SmPC for the full list of contraindications and precautions.

It is important to note that immunotherapy is allergen-specific. Mixing non-homologous allergens (e.g., birch and grass) in a single SLIT or SCIT preparation is not routine practice; patients sensitised to multiple unrelated allergens should be assessed by a specialist, following BSACI guidance, to determine the most appropriate treatment approach.

Sources: MHRA/EMC SmPC for ITULAZAX; EMA EPAR for ITULAZAX; BSACI guideline on allergen immunotherapy.

OTC Medications Available for Tree Pollen Allergy Relief

A wide range of over-the-counter (OTC) medications is available in the UK to manage tree pollen allergy symptoms. These treatments are effective at controlling symptoms but do not alter the underlying allergic disease. The main categories include:

Antihistamines Oral antihistamines are typically the first-line OTC option. Second-generation antihistamines — such as cetirizine, loratadine, and fexofenadine — are preferred over first-generation options (e.g., chlorphenamine) as they cause less sedation. They work by blocking H1 histamine receptors, reducing sneezing, itching, and rhinorrhoea. They are generally well tolerated, though some individuals may still experience mild drowsiness.

Intranasal corticosteroids Sprays such as beclometasone, fluticasone, and mometasone are available OTC and are considered highly effective for nasal symptoms. They work by reducing local inflammation in the nasal mucosa. NICE guidance supports their use as a first-line treatment for moderate-to-severe allergic rhinitis, and they are often more effective than antihistamines alone for nasal congestion. For best effect, intranasal corticosteroids should be used regularly every day — they may take several days of consistent use to reach their full effect, so starting treatment before the pollen season begins is advisable.

Eye drops For ocular symptoms, OTC eye drops can provide targeted relief. Ketotifen eye drops are an antihistamine option. Sodium cromoglicate eye drops are also widely used; these act as a mast cell stabiliser (not an antihistamine) and work by preventing the release of inflammatory mediators. Both are available without prescription.

Decongestants Oral or nasal decongestants (e.g., pseudoephedrine, xylometazoline) may offer short-term relief from nasal congestion. Topical nasal decongestants should not be used for more than 7 days continuously, as prolonged use carries a risk of rebound congestion (rhinitis medicamentosa). Patients with hypertension or cardiovascular conditions should seek pharmacist or GP advice before using decongestants.

Suspected side effects from any OTC medicine should be reported to the MHRA via the Yellow Card Scheme (yellowcard.mhra.gov.uk).

Sources: NICE CKS: Allergic rhinitis; BNF; NHS hay fever medicines page.

Comparing Effectiveness: Immunotherapy Versus OTC Treatments

When comparing immunotherapy with OTC medications, it is important to consider both the nature and the durability of the benefit. OTC treatments are effective at managing symptoms on a day-to-day basis and are appropriate for many patients with mild-to-moderate allergic rhinitis. However, they require ongoing use throughout the pollen season and provide no lasting benefit once discontinued. It is also worth noting that head-to-head comparisons between AIT and optimally used intranasal corticosteroid regimens are limited; immunotherapy is generally considered when pharmacotherapy has proved inadequate.

Immunotherapy, by contrast, offers several distinct advantages for suitable patients:

• Disease modification: It addresses the root cause of the allergy rather than masking symptoms.

• Sustained benefit: Clinical studies, including data from the ITULAZAX development programme, have demonstrated that symptom relief can persist for several years after completing a course of treatment.

• Reduced medication burden: Many patients experience a significant reduction in their need for antihistamines and nasal sprays during and after immunotherapy.

• Possible prevention of progression: There is some evidence, particularly in paediatric populations, that immunotherapy may reduce the risk of developing new sensitisations and lower the likelihood of allergic rhinitis progressing to asthma. However, this evidence is not definitive across all patient groups and allergens, and results vary; patients should discuss this with their specialist.

Immunotherapy is not without limitations. It requires a substantial time commitment — typically weekly or fortnightly clinic visits for SCIT during the build-up phase — and results are not immediate, with meaningful improvement often taking several months. There is also a small but recognised risk of allergic reactions, particularly with SCIT, which is why it must be administered in a supervised clinical setting with resuscitation facilities available, as per MHRA and NHS guidance. For patients with mild, well-controlled symptoms, OTC medications may remain the most practical and cost-effective option.

Sources: BSACI guideline on allergen immunotherapy; EMA EPAR and MHRA/EMC SmPC for ITULAZAX; NICE CKS: Allergic rhinitis.

NICE Guidelines and NHS Access to Allergy Immunotherapy

NICE has issued guidance supporting the use of allergen immunotherapy for allergic rhinitis in specific circumstances. A NICE Technology Appraisal recommends grass pollen sublingual immunotherapy (specifically the GRAZAX tablet) as an option for adults with severe grass pollen-induced rhinitis that has not responded adequately to standard pharmacotherapy. Readers should consult the current NICE Technology Appraisal for GRAZAX and NICE CKS: Allergic rhinitis for the most up-to-date commissioning and management guidance, as recommendations are subject to review. For tree pollen allergy, the evidence base and NHS commissioning landscape continue to evolve.

In England, access to immunotherapy for tree pollen allergy — including birch pollen SLIT or SCIT — is generally available through NHS specialist allergy clinics, though provision varies by region and waiting times can be lengthy. Patients are typically referred by their GP to an NHS allergy service, where a full clinical assessment, including skin prick testing or specific IgE blood tests, is carried out to confirm the diagnosis and identify the relevant allergens before any immunotherapy is considered.

The British Society for Allergy and Clinical Immunology (BSACI) provides clinical guidelines that support the use of AIT for tree pollen allergy in appropriately selected patients, particularly those with moderate-to-severe symptoms inadequately controlled by pharmacotherapy. The birch pollen SLIT tablet ITULAZAX holds a UK licence for adults and has been evaluated by the EMA; patients and clinicians should refer to the current SmPC for full prescribing information, including indication, dosing schedule, and contraindications.

Patients who are unable to access NHS immunotherapy may explore private allergy clinics, though costs can be considerable. Local NHS commissioning policies should be checked, as funding arrangements vary across regions.

Sources: NICE Technology Appraisal (GRAZAX); NICE CKS: Allergic rhinitis; BSACI rhinitis and immunotherapy guidelines; MHRA/EMC SmPC for ITULAZAX; EMA EPAR for ITULAZAX.

Choosing the Right Treatment: When to Seek Specialist Advice

For many people with tree pollen allergy, a stepwise approach to management is appropriate. Mild symptoms that respond well to OTC antihistamines and intranasal corticosteroids may not require specialist input. However, there are clear circumstances in which a GP referral to an allergy specialist should be considered:

• Symptoms that are severe or significantly impact quality of life, including sleep disturbance, impaired concentration, or inability to work or study

• Inadequate response to two or more OTC or prescribed medications used correctly

• Co-existing asthma that worsens during tree pollen season

• Diagnostic uncertainty — for example, perennial symptoms that may suggest a different allergen trigger

• Interest in or suitability for allergen immunotherapy

• A history of anaphylaxis or severe allergic reactions

Important: AIT should not be started in patients with uncontrolled asthma, and it must always be initiated and supervised in a specialist clinical setting. If at any point a patient experiences severe breathing difficulty, wheeze, throat tightening, or other signs of anaphylaxis — whether related to AIT or any other cause — they should call 999 immediately and use an adrenaline auto-injector if one has been prescribed.

Patients should be advised to keep a symptom diary noting the timing and severity of their symptoms, as this information is valuable for both diagnosis and treatment planning.

Tree pollen allergy — particularly in birch-sensitised individuals — can be associated with oral allergy syndrome (pollen-food syndrome), in which itching or tingling occurs in the mouth when eating certain raw fruits (e.g., apples, peaches), vegetables, or nuts (e.g., hazelnuts). Cooked or processed forms of these foods are often tolerated. If systemic symptoms occur (e.g., throat swelling, hives, or breathing difficulty) after eating these foods, medical advice should be sought promptly, as this may indicate a more significant food allergy requiring specialist assessment.

Ultimately, the decision between continuing OTC management and pursuing immunotherapy should be made collaboratively between the patient and their healthcare team, taking into account symptom severity, lifestyle impact, treatment goals, and individual suitability. Immunotherapy represents a meaningful long-term investment for those with persistent, troublesome tree pollen allergy, whilst OTC medications remain a valuable and accessible option for day-to-day symptom control.

Any suspected side effects from prescribed or OTC medicines should be reported to the MHRA via the Yellow Card Scheme (yellowcard.mhra.gov.uk).

Sources: NICE CKS: Allergic rhinitis; BSACI rhinitis and pollen-food syndrome guidance; BSACI allergen immunotherapy guideline; NHS anaphylaxis page; MHRA Yellow Card Scheme.

Frequently Asked Questions