Allergy immunotherapy: injections, tablets and treatment commitment
Allergy immunotherapy repeatedly exposes the immune system to a specific allergen under medical supervision. Injections and under-the-tongue products use different schedules and precautions, but both require a confirmed clinically relevant allergy and sustained adherence. They are not quick substitutes for antihistamines, and an anti-allergy biologic such as omalizumab is a different treatment rather than another delivery form of immunotherapy.
Key takeaways
- A positive allergy test is not enough: the result must fit the person’s symptoms, exposure pattern and medical history.
- Subcutaneous injections and sublingual tablets or drops differ in where they are given, their common reactions and how much clinic attendance they require.
- Treatment commonly continues for years, and serious allergic reactions are possible, so suitability and an emergency plan matter as much as convenience.
What is allergy immunotherapy trying to change?
Usual allergic-rhinitis medicines reduce symptoms or inflammation during exposure. Allergen immunotherapy instead gives controlled, repeated exposure to an allergen with the aim of changing the immune response over time. It may be considered when a specific trigger such as house-dust mite or pollen is clearly linked to significant symptoms and ordinary measures have not provided acceptable control or are difficult to sustain.
The assessment is more than ordering a panel of tests. Skin-prick or specific-IgE results show sensitisation, which does not always mean that an allergen causes the symptoms. Timing, home and work exposures, nasal or eye symptoms, asthma control, previous reactions and current treatment help determine whether a result is clinically relevant. The Australasian Society of Clinical Immunology and Allergy (ASCIA) describes immunotherapy as specialist treatment selected for the allergens causing the person’s problem, not a general treatment for every positive result.
How do injections and under-the-tongue treatment differ?
| Question | Subcutaneous immunotherapy (SCIT) | Sublingual immunotherapy (SLIT) |
|---|---|---|
| How is the allergen given? | An injection under the skin, with a build-up phase followed by maintenance treatment | A tablet or liquid held under the tongue, usually on a regular home schedule after supervised initiation |
| Where is it given? | In a medical setting equipped to recognise and treat systemic reactions | Product- and jurisdiction-dependent; the first dose of licensed tablets is commonly supervised, with later doses at home |
| Common local effects | Redness, itch or swelling around the injection site | Mouth or throat itch, irritation or swelling, especially early in treatment |
| Main practical burden | Repeated clinic visits and an observation period after injections | Remembering consistent home treatment and following the exact product instructions |
| Serious risk | Systemic allergic reaction, including anaphylaxis | Less common than local mouth symptoms, but severe allergic reactions can still occur |
The table does not establish which route is suitable. Available allergen products, age limits, asthma status, other medicines, pregnancy and willingness to follow the schedule all change the choice. The AAAAI allergy-tablet guide notes that licensed tablet instructions are allergen-specific; a dust-mite tablet cannot be assumed to cover another trigger.
Singapore allergy services assess and supervise immunotherapy rather than treating it as a retail allergy product. For example, KK Women’s and Children’s Hospital lists allergen testing, suitability assessment, protocol supervision and management of reactions within its allergy service. Availability and exact instructions should therefore be confirmed with the treating service rather than inferred from an overseas product page.
Why does treatment take so long?
Immunotherapy depends on repeated exposure over a prolonged period. Injection treatment has an initial build-up and a maintenance phase; sublingual treatment requires regular dosing. The full course is commonly measured in years rather than weeks. Missed visits or frequent missed home doses can reduce continuity and may require the treating service to reconsider how treatment is resumed.
Early symptom improvement is not proof that the course is complete, and lack of immediate change is not a reason to increase exposure independently. Reviews consider symptom burden, rescue-medicine use, reactions, adherence and whether the original allergen remains the right target. A person still needs an ordinary plan for breakthrough rhinitis or asthma symptoms while immunotherapy is underway; see allergic rhinitis medicines and the allergy-relief category.
Is omalizumab another type of allergy immunotherapy?
No. Allergen immunotherapy administers a selected allergen. Omalizumab is a biologic medicine that binds free IgE and is used for particular approved conditions and patient groups. It does not identify or deliver the causal allergen, and it should not be presented as a routine companion that makes immunotherapy universally safer or more effective.
Specialists may use a biologic and allergen immunotherapy in selected complex cases, but that is a separate risk–benefit decision. The legacy article’s claim that omalizumab routinely “enhances” immunotherapy was not retained because it turns a specialist strategy into a general recommendation.
Which reactions need urgent help?
Local redness after an injection or temporary mouth itch with a sublingual product can occur, but the treatment team should explain what to record and when to contact them. Widespread hives, swelling of the tongue or throat, breathing difficulty, wheeze, faintness, collapse or rapidly worsening symptoms can indicate anaphylaxis and need emergency care.
Do not take an extra dose, change an injection interval or restart after a significant reaction without instructions from the treating service. Asthma symptoms on a treatment day also matter because poorly controlled asthma can increase the danger of a systemic reaction.
What changes the answer?
- The allergen and evidence of exposure. The available product must match a trigger that actually explains the symptoms.
- Asthma control. Current wheeze, recent attacks or reduced lung function may alter whether treatment proceeds that day or at all.
- Age and product licence. Age ranges differ between products and countries; overseas approval cannot establish Singapore suitability.
- Pregnancy or pregnancy planning. Immunotherapy is generally not newly started during pregnancy, while continuation decisions require the treating specialist.
- Other conditions and medicines. Cardiovascular disease, previous anaphylaxis and medicines that complicate treatment of a severe reaction require discussion.
- Ability to follow the programme. Clinic access, travel, daily routines and understanding the emergency plan influence whether a route is realistic.
What should you ask at the assessment?
Bring the symptom timeline, previous test results, inhalers and allergy medicines, details of reactions, and a complete medicine list. Ask which allergen is being targeted, what evidence links it to symptoms, which product and route are proposed, where doses are taken, what happens after a missed dose, which reactions require contact or emergency help, and how benefit will be reviewed.
The allergic-rhinitis condition page can help organise the diagnosis and ingredient names. It cannot determine whether a particular allergen extract is appropriate for an individual.
Sources
- Australasian Society of Clinical Immunology and Allergy: Allergen immunotherapy.
- American Academy of Allergy, Asthma & Immunology: What you need to know about allergy tablets.
- American Academy of Allergy, Asthma & Immunology: Hay fever and rhinitis.
- HealthHub Singapore / KKH: Allergy services.
