Under-the-tongue allergy treatment (sublingual immunotherapy)
A daily tablet or drops placed under the tongue that, over years, makes your immune system react less to an allergen such as grass pollen or house dust mite.
✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review
In short
- Under-the-tongue treatment aims to make your immune system react less to an allergen such as grass pollen or house dust mite; it reduces symptoms but does not always cure the allergy.
- The first dose is given and watched in a clinic; later daily doses are taken at home, with advice on what to do if you react.
- Side effects are usually mild — most often tingling or itching in the mouth in the first weeks — but it must be taken daily for about three years to work.
- It is used when symptoms are severe and avoidance and ordinary medicines have not worked, not as a first step.
A plain-English summary. The detail — including risks and recovery — is below.
At a glance
A general guide. Your specialist will give you advice for your situation.
Can reduce hay fever or dust mite symptoms and the need for antihistamines and steroid sprays
You have severe or poorly controlled asthma.
You take the dose and are watched for a period, commonly around 30 minutes to an hour, so any reaction can be treated. Tell staff if your mouth, throat or...
A supervised first dose with a monitoring period and emergency treatment ready.
You take the dose and are watched for a period, commonly around 30 minutes to an hour, so any reaction can be...
Tingling, itching or mild swelling in the mouth is common and usually settles. An antihistamine taken beforehand...
Symptoms often begin to improve, though it can take a full season to notice a clear difference.
Daily dosing continues. Pause as advised for mouth ulcers, dental work or illness, then restart as instructed.
What is sublingual immunotherapy (under-the-tongue allergy treatment)?
Sublingual immunotherapy (SLIT) is a treatment that slowly teaches your immune system to react less to something you are allergic to. You take a tablet, or sometimes drops, that contains a small amount of the allergen and hold it under your tongue before swallowing. It is taken every day, usually for about three years.
It is mainly used in the UK for severe grass-pollen hay fever and for house dust mite allergy, when avoiding the allergen and ordinary medicines such as antihistamines and steroid nasal sprays have not controlled symptoms well enough. The aim is to reduce symptoms and the need for other medicines, not always to remove the allergy completely.
The very first dose is given in a clinic and you are watched for a period afterwards, because a reaction is possible. After that, if the first dose was well tolerated, you take it at home each day. Your specialist will explain what to do if you feel unwell and may give you a rescue plan.
SLIT generally causes milder side effects than allergy injections — most often tingling, itching or mild swelling in the mouth in the first couple of weeks. It still takes a long-term commitment to work.
Types, options & approaches
There may be different ways to do this. The right approach depends on the clinical question and your circumstances.
Under-the-tongue treatment (SLIT) vs allergy injections (SCIT)
| Point | Under the tongue (SLIT) | Injections (SCIT) |
|---|---|---|
| How it is given | Tablet or drops under the tongue | Injection under the skin |
| Where | First dose in clinic, then at home | Every dose in a specialist clinic |
| Main side effects | Mostly mild mouth tingling or itching | Local swelling; small risk of whole-body reaction |
| Suits | Mainly grass pollen and dust mite | Pollen, insect venom and some others |
Both take about three years and both reduce rather than always abolish symptoms. Your specialist will advise which suits your allergy.
Preparing for your treatment
- See a specialist first; the allergy is usually confirmed with skin prick or blood (specific IgE) tests and a careful history.
- Tell the team about asthma — it should be well controlled, as treatment is not started during an asthma flare.
- Mention any mouth ulcers, recent dental work or loose teeth, as treatment is paused while the mouth heals.
- Tell them if you are or might be pregnant — a new course is not usually started in pregnancy.
- For seasonal allergens such as grass pollen, expect to start several weeks to months before the season.
- Plan for the first dose to be given in clinic, where you will be watched for a period afterwards.
- Be ready to take it every single day for about three years for it to work.
What happens
Your specialist confirms the allergy and decides whether sublingual immunotherapy is suitable. The first dose is given in a clinic with resuscitation facilities, because a reaction is possible. You place the tablet or drops under your tongue, hold it there for a minute or two, then swallow, and you are watched for a period afterwards — commonly around 30 minutes to an hour.
If the first dose is well tolerated, you take it at home each day. You are asked not to eat or drink for about five minutes before and after each dose. Mild tingling or itching in the mouth is common in the first couple of weeks and usually settles.
You continue daily for about three years. The team gives you advice on side effects, when to pause treatment (for example after dental work or with a mouth ulcer), and what to do if you have a more troublesome reaction.
Is this treatment right for me?
A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.
May not be suitable if…
- You have severe or poorly controlled asthma.
- Your allergy is mild and well controlled by avoidance and medicines.
- You have a mouth condition, severe oral inflammation or recent significant dental surgery (treatment may be delayed rather than ruled out).
- You cannot commit to taking a daily dose for about three years.
- The allergen you react to is not one for which a suitable, licensed sublingual treatment exists.
Delay or rearrange if…
- Your asthma is currently flaring or poorly controlled.
- You have a mouth ulcer, open sore or have had recent dental work or tooth loss.
- You are unwell with a fever or significant infection.
- You are pregnant or might become pregnant — a new course is not usually started in pregnancy.
- The allergy has not yet been confirmed by testing.
Alternatives to discuss
- Allergen avoidance measures, which are first-line for house dust mite allergy.
- Regular antihistamines and steroid nasal sprays for hay fever symptoms.
- Allergy injections (subcutaneous immunotherapy) for some allergens or where tablets are unsuitable.
- No immunotherapy, if symptoms are mild or you prefer to manage with medicines.
- A different specialist opinion if the diagnosis or best option is unclear.
Before you decide
Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.
What matters most to me?
Think about symptoms, daily life, work, caring responsibilities, sport, fertility, travel, appearance and anxiety — the right choice depends on your priorities, not just the medical facts.
What are all my options?
Ask about waiting, monitoring, medicines, rehabilitation, a smaller or larger procedure, a different test, NHS referral, or a second opinion where that would help.
What would make me pause?
Active infection, pregnancy, unstable medical problems, smoking, medicines that increase bleeding, poor support at home, or feeling pressured are all reasons to slow down and get tailored advice.
What happens if I do nothing today?
For some problems, waiting is safe; for others, delay can make treatment harder. A good consultation should explain the trade-off in plain English.
Benefits
- Can reduce hay fever or dust mite symptoms and the need for antihistamines and steroid sprays
- Taken at home after the first dose, so fewer clinic visits than injections
- Generally causes milder side effects than allergy injections
- Is one of the few treatments that changes the underlying allergy rather than just masking symptoms
- Benefit can last for some years after a full course is completed
Risks & complications
- Tingling, itching or mild swelling in the mouth, lips or under the tongue, mainly in the first couple of weeks
- An itchy or irritated throat or ears
- Mild stomach upset
- The need to take it every day for years
- More marked mouth or throat swelling that needs treatment or a pause
- Worsening of asthma symptoms
- Mouth discomfort that makes it hard to continue
- A severe allergic reaction (anaphylaxis), which is why the first dose is given under supervision
- A severe throat swelling affecting breathing or swallowing
Most side effects are mild mouth and throat symptoms in the first weeks. A severe reaction is rare but possible, which is why the first dose is supervised and you are given a plan for what to do at home. Risk is higher if your asthma is poorly controlled. Ask what symptoms should make you stop and seek help, and whether you should be given a rescue plan or adrenaline auto-injector.
Published figures to discuss
Most side effects are mild local reactions in the mouth and throat, especially in the first two weeks, and often settle without stopping treatment. Serious whole-body reactions are rare with sublingual treatment, but the first dose is supervised because they can happen. Exact figures vary by product and allergen.
| Figure | Reported range | How to interpret it | Source / confidence |
|---|---|---|---|
| Local mouth or throat reactions | Common, especially in the first 1-2 weeks | Tingling, itching or mild swelling in the mouth or throat. Usually mild and settles, sometimes helped by an antihistamine taken beforehand. | Guide sourcesClinical context |
| Treatment stopped because of side effects | A minority of people | Mostly because of persistent or troublesome mouth and throat symptoms rather than serious reactions. | NHS — Allergies: treatmentnhs.ukSource-linked context |
| Anaphylaxis | Rare, but important | The reason the first dose is given under supervision and a rescue plan is provided for home dosing. | Guide sourcesClinical context |
These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.
What happens afterwards
There is no physical recovery. The first dose is watched in clinic, then the treatment fits into daily life — but it needs to be taken every day for about three years to work.
- Tingling, itching or mild swelling in the mouth in the first couple of weeks
- An itchy throat or ears after a dose
- Mild, short-lived stomach upset
- Slow, gradual improvement in symptoms over a season rather than overnight
Aftercare
- Take the dose at the same time each day and hold it under the tongue as instructed before swallowing.
- Do not eat or drink for about five minutes before and after each dose.
- Take an antihistamine beforehand in the first weeks if advised, to ease mouth symptoms.
- Pause treatment after dental work or tooth loss, or if you have a mouth ulcer or open sore, until it heals.
- Pause if you are unwell with a fever and restart as your specialist advised.
- Keep your asthma well controlled and take your asthma medicines as prescribed.
- Know your rescue plan and carry any adrenaline auto-injector you have been given.
- Allergy confirmed by testing, not just assumed
- Asthma reviewed and well controlled before starting
- First dose appointment in clinic arranged
- Clear instructions on when to pause (dental work, mouth ulcers, illness)
- A written rescue plan, and an adrenaline auto-injector if prescribed
- A reminder system so you take it every day
- Clinic contact number saved for problems at home
⚠ Get urgent help if…
- Marked swelling of the lips, tongue or throat, or trouble swallowing
- Difficulty breathing, wheeze or a tight chest
- Widespread hives, flushing or severe itching
- Feeling faint, dizzy or collapsing
- Severe or persistent mouth or throat swelling after a dose
- Severe stomach pain or repeated vomiting after doses
Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.
General guidance — it doesn't replace the specific advice your specialist gives you.
Results & realistic expectations
A good result means your hay fever or dust mite symptoms are noticeably better and you need less day-to-day medicine. Improvement usually builds over the first season or year rather than immediately. Even a successful course may reduce rather than completely remove symptoms, and the response varies from person to person. Your specialist will review progress over the first year and over the full course.
After a full course of about three years, many people keep their improvement for several years. Some find symptoms slowly return and may be offered further treatment. Stopping early, before three years, makes a lasting benefit less likely.
Related tests, treatments or support
Under-the-tongue treatment is used alongside, not instead of, allergen avoidance and your usual allergy medicines, especially early on. For house dust mite allergy, avoidance measures remain important. If you are allergic to more than one thing, your specialist will decide what to treat and in what order.
Follow-up & long-term care
Your specialist reviews how you tolerated the first dose, your symptoms, your asthma control and any side effects, with further reviews through the course. Towards the end of about three years they discuss whether to stop and what to expect afterwards.
- A daily dose under the tongue for about three years
- Pausing and restarting around dental work, mouth ulcers or illness as advised
- Ongoing review of asthma control
- Keeping and replacing any prescribed adrenaline auto-injector before it expires
- Continued allergen avoidance and usual medicines alongside the treatment
Repeat, follow-on and what comes next
- Treatment is often paused and restarted around dental work, mouth ulcers or illness.
- If symptoms return after a completed course, a specialist may consider further treatment.
- Some people cannot tolerate the mouth symptoms and switch to another approach or stop.
- Stopping before three years makes lasting benefit less likely.
Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.
What good aftercare looks like
- A supervised first dose with a monitoring period and emergency treatment ready.
- A clear written rescue plan for reactions at home, and an adrenaline auto-injector if needed.
- Plain advice on when to pause treatment and how to restart.
- Regular review of symptoms, asthma control and tolerance.
- An honest discussion at the end of the course about benefit and the chance of symptoms returning.
What affects the cost
Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:
- The specialist assessment and ongoing review fees
- The cost of the daily tablet or drops, which is ongoing over about three years
- Allergy testing to confirm the diagnosis before starting
- The first-dose clinic visit with its monitoring period
- Any extra treatment needed to control asthma before and during the course
- The total length of treatment, usually about three years
- The consultant and clinic fees for assessment and review
- The cost of the medicine and how long the course will run
- Whether the price covers the supervised first dose and its monitoring
- Whether ongoing prescriptions are included or charged separately
- What happens, and what it costs, if you cannot tolerate the treatment
- The cancellation and refund policy if treatment is stopped early
On the NHS? Some under-the-tongue treatments are available on the NHS, started by a specialist, when symptoms are severe and other treatments have not worked; private care may be used for faster access or choice of clinic.
You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.
Consent traps and marketing red flags
These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.
Consent traps
- Not being told that the first dose must be supervised and why.
- Not being given a clear plan for what to do if a reaction happens at home.
- Starting without asthma being assessed and controlled.
- Being led to expect a cure rather than a reduction in symptoms.
- Not discussing the three-year daily commitment and the chance of stopping early.
Marketing red flags
- Selling allergy tablets or drops online without a specialist assessment or supervised first dose.
- Promising a guaranteed cure or complete end to your allergy.
- Starting treatment without confirming the allergy by proper testing.
- Offering unlicensed products without explaining the lack of regulatory approval.
- Pushing immunotherapy for a mild allergy that medicines already control.
Choosing a specialist safely
- Check the specialist is on the GMC Specialist Register for this area.
- Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
- You're entitled to time to consider and to have your questions answered before you agree — the specialist who looks after you should explain it, not a salesperson.
- Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
- You're entitled to your total cost in writing — including any follow-up — before you decide.
Questions to ask your medical professional
Take this to your consultation. A good specialist will welcome every one of these.
- Has my allergy been confirmed by testing, and is this treatment likely to help me?
- How much improvement can I realistically expect, and when will we know if it is working?
- What side effects should I expect, and what should make me stop and seek help?
- Is my asthma well enough controlled to start safely?
- Will I be given a rescue plan or an adrenaline auto-injector to keep at home?
- What happens at the end of the course, and could my symptoms come back?
- Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
- Will you be the specialist who carries out my treatment, and who looks after me afterwards?
- What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
- What does a realistic result look like — and what can this treatment not achieve?
- What are my options, including waiting, doing nothing for now, or choosing a different approach?
- Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
- What is the total cost in writing, including any follow-ups, and how much time do I have to decide?
Frequently asked questions
Why is the first dose given in a clinic if I take the rest at home?
Is it available on the NHS?
How long do I have to take it?
Will it cure my allergy?
What are the side effects?
Is it better than allergy injections?
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How we made this page
Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →
Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.
Sources & standards: NHS — Allergies: treatment Allergy UK — Immunotherapy factsheet BSACI — SOP: Administration of sublingual immunotherapy (SLIT) NICE TA1045 — House dust mite SLIT for allergic rhinitis BSACI — Immunotherapy for allergic rhinitis guideline
Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.
Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.
Related guides: Allergy injections (subcutaneous immunotherapy) · House dust mite allergy management · Pet (animal) allergy management · Bee and wasp sting allergy testing and treatment · Anaphylaxis assessment and adrenaline pen training