Early SLIT Immunotherapy for Hay Fever and Asthma Prevention London
13th May 2026
SLIT Immunotherapy London
Early SLIT Immunotherapy: Could Treating Hay Fever Earlier Help Protect Against Asthma?
New medical evidence suggests that sublingual allergen immunotherapy (SLIT) may be more than symptom control. For carefully selected patients, it may help change the long-term course of allergic rhinitis and allergic asthma.
Key message
SLIT immunotherapy is increasingly being viewed as a disease-modifying treatment for allergic rhinitis and allergic asthma, rather than only a final option when antihistamines and nasal sprays are not enough.
What is SLIT immunotherapy?
Sublingual allergen immunotherapy (SLIT) is a specialist allergy treatment designed to gradually train the immune system to tolerate a specific allergen. It may be used for selected patients with allergic rhinitis, allergic conjunctivitis and allergic asthma caused by triggers such as grass pollen, tree pollen, house dust mite or animal dander.
Unlike standard medicines, which mainly reduce symptoms while they are being taken, SLIT aims to reduce the body’s allergic response over time. Treatment is usually administered as liquid allergen drops under the tongue according to the prescribed treatment plan.
How SLIT works
Small amounts of allergen are introduced regularly under the tongue to encourage immune tolerance over time. The treatment plan is individualised according to the allergen profile, symptoms and medical history.
Why is earlier treatment being discussed?
A 2026 expert review in Current Opinion in Allergy and Clinical Immunology highlights a shift in thinking. Traditionally, allergen immunotherapy was often considered only after symptoms remained troublesome despite medication. However, newer real-world evidence suggests that starting immunotherapy earlier in suitable patients may offer a “window of opportunity” to influence the natural history of allergic airway disease.
This is particularly relevant for patients with persistent allergic rhinitis, with or without mild to moderate allergic asthma. Allergic rhinitis and asthma are closely linked, and untreated or poorly controlled nasal allergy may contribute to lower airway symptoms in some patients.
Potential benefits of earlier SLIT immunotherapy
- Reduced need for long-term allergy medication
- Improved control of allergic rhinitis symptoms
- Fewer severe asthma exacerbations in some patient groups
- Possible reduction in the risk of developing asthma
- Possible reduction in the development of new allergen sensitisation
- Long-lasting benefit after completion of treatment in selected patients
What does recent evidence show?
Large real-world studies, including the REACT programme and the EfficAPSI study, suggest that adding allergen immunotherapy to standard care may reduce medication use, severe asthma exacerbations and healthcare use over long-term follow-up.
The 2026 review also highlights that younger patients may gain particular benefit when treatment is started before allergic airway disease becomes more established. This supports the idea that allergic rhinitis should not always be viewed as a minor condition, especially when symptoms are persistent, seasonal year after year, or associated with wheeze, cough or exercise-related breathing symptoms.
Who may be suitable for SLIT immunotherapy?
SLIT is not suitable for everyone. It should only be considered after specialist allergy assessment, including a careful clinical history and confirmation that symptoms match relevant IgE sensitisation on skin prick testing or blood testing.
You may be considered if you have:
- Moderate to severe hay fever
- Persistent house dust mite allergy
- Allergic rhinitis with confirmed pollen, mite or animal allergy
- Symptoms despite regular antihistamines or nasal sprays
- Allergic asthma that is mild to moderate and controlled enough for treatment
A specialist review is essential if you have:
- Uncontrolled asthma
- A history of severe allergic reactions
- Multiple allergies requiring prioritisation
- Other medical conditions or regular medication
- Uncertainty about the main allergen causing symptoms
Why accurate diagnosis matters
The success of SLIT depends on selecting the correct allergen. For example, a patient with spring symptoms may be reacting to birch pollen, grass pollen, plane tree pollen, or more than one pollen. A patient with year-round symptoms may have house dust mite allergy, animal dander allergy, mould allergy, non-allergic rhinitis, or a combination of causes.
At a consultant-led allergy clinic, testing may include skin prick testing, specific IgE blood testing and, where appropriate, molecular allergy testing. This helps confirm whether immunotherapy is likely to be clinically relevant and which allergen should be prioritised.
Early treatment does not mean rushed treatment
Earlier SLIT means considering disease-modifying treatment before allergic disease progresses further. It does not mean starting treatment without proper assessment. The allergen profile, safety considerations and asthma control must all be reviewed carefully.
How long does treatment take?
SLIT immunotherapy is usually a long-term commitment. Many treatment courses continue for around three years, depending on the allergen and clinical response. The aim is to achieve sustained immune tolerance and longer-lasting benefit, rather than short-term symptom relief only.
Can SLIT replace antihistamines and nasal sprays?
Not immediately. Symptomatic treatment remains important, especially during the early stages of immunotherapy and during high pollen exposure. Many patients continue to use nasal sprays, antihistamines or eye drops as needed. Over time, some patients may need less medication, but this should be reviewed individually.
Why choose a specialist allergy clinic?
SLIT should be prescribed and monitored by clinicians experienced in allergy diagnosis, asthma assessment and immunotherapy safety. A specialist clinic can help identify the most relevant allergen, assess asthma risk and monitor response throughout the course.
Considering SLIT immunotherapy for hay fever, dust mite allergy or allergic asthma?
A consultant-led allergy assessment can help determine whether SLIT immunotherapy is appropriate for you or your child.
Summary
SLIT immunotherapy is increasingly recognised as a treatment that may modify the course of allergic respiratory disease. For suitable patients with confirmed allergic rhinitis, and especially those at risk of asthma progression, earlier discussion of immunotherapy may be clinically valuable.
The decision should always be personalised. The most important first step is accurate diagnosis, followed by careful selection of the correct allergen treatment plan.
Medical disclaimer: This article is for general information only and does not replace medical advice. Immunotherapy should only be started after assessment by an appropriately qualified allergy specialist.
References include: Lombardi C. et al. Allergen-specific immunotherapy at earlier stages of allergic respiratory diseases. Current Opinion in Allergy and Clinical Immunology. 2026; ARIA-EAACI allergic rhinitis guidance; AAAAI, London Allergy and Immunology Centre’s patient information on allergy immunotherapy.
