Allergy injections (subcutaneous immunotherapy)
A course of injections of a small, gradually increasing amount of an allergen, given in a specialist clinic to make your immune system react less strongly to it over time.
✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review
In short
- Allergy injections aim to make your immune system react less to an allergen such as pollen or insect venom; they reduce symptoms but do not always cure the allergy.
- They carry a small but real risk of a serious allergic reaction, so they are only given in a specialist clinic with a waiting period and resuscitation equipment on hand — never at home.
- A full course usually runs for about three years, so you need to be able to attend regularly.
- They are used when an allergy is severe and ordinary treatments and avoidance 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 symptoms and the need for antihistamines and steroid sprays in severe pollen allergy
You have severe or poorly controlled asthma, which makes a serious reaction more likely and more dangerous.
You wait in the clinic, usually for about an hour, while staff watch for any reaction. Tell them at once if you feel unwell, itchy, wheezy or your mouth...
A monitoring period in clinic after every injection, with adrenaline and resuscitation equipment ready.
You wait in the clinic, usually for about an hour, while staff watch for any reaction. Tell them at once if you...
A local swelling at the injection site, tiredness or mild flu-like feelings can appear later in the day and...
Injections of increasing strength, often weekly. Reaction risk is highest now, so close monitoring continues at...
Once at the top dose, injections are spread out to every few weeks. Symptoms often begin to ease over the first...
What is subcutaneous immunotherapy (allergy injections)?
Subcutaneous immunotherapy (SCIT), often called allergy injections or desensitisation, is a treatment that slowly teaches your immune system to react less to something you are allergic to, such as grass pollen, tree pollen or wasp and bee venom. A specialist gives you injections containing a tiny amount of the allergen, and the dose is increased step by step over time.
It is not a quick fix and it is not for everyone. It is used when an allergy is genuinely affecting your life, when ordinary treatments like antihistamines and steroid nasal sprays have not controlled symptoms, and when avoiding the allergen is not enough. The aim is to reduce how badly you react, not always to make the allergy disappear completely.
The injections carry a real, if small, risk of a serious allergic reaction (anaphylaxis). For this reason they are always given in a specialist clinic, where you are watched for a period afterwards and where staff and equipment to treat a reaction are immediately available. They are never given to take home and inject yourself.
A full course usually takes about three years, and you need to be able to commit to attending regularly.
Types, options & approaches
There may be different ways to do this. The right approach depends on the clinical question and your circumstances.
Allergy injections (SCIT) vs under-the-tongue treatment (SLIT)
| Point | Injections (SCIT) | Under the tongue (SLIT) |
|---|---|---|
| How it is given | Injection under the skin | Tablet or drops under the tongue |
| Where | Every dose in a specialist clinic | First dose in clinic, then at home |
| Serious reaction risk | Small but real, watched in clinic | Lower; mostly mild mouth symptoms |
| Suits | Pollen, insect venom and some others | Mainly grass pollen and dust mite |
Both take years and both reduce rather than always abolish symptoms. Your specialist will advise which is suitable for your allergy.
Preparing for your treatment
- See a specialist in an allergy clinic first; the diagnosis is usually confirmed with skin prick or blood (specific IgE) tests and a careful history.
- Tell the team about asthma — poorly controlled asthma makes injections more dangerous and must be stabilised first.
- List all your medicines; some, such as beta-blockers and ACE inhibitors, can make a reaction harder to treat and may need review.
- Tell them if you are or might be pregnant — a new course is not usually started in pregnancy.
- Plan for the time commitment: frequent visits during the early build-up phase, then regular maintenance injections for about three years.
- Expect to stay in the clinic for about an hour after every injection, so allow time and do not plan to rush off.
- Avoid heavy exercise, hot baths and alcohol around the time of each injection, as these can increase the chance of a reaction.
What happens
Treatment has two phases. In the build-up phase you have injections of gradually increasing strength, often weekly at first. Once you reach the top (maintenance) dose, injections are spaced further apart, typically every few weeks, and continued for about three years.
Each injection is given just under the skin, usually in the upper arm, by a nurse or doctor in a specialist clinic. Before the injection the team checks you are well, that your asthma is controlled if you have it, and reviews any reaction to the last dose.
After every injection you wait in the clinic, usually for about an hour, so that staff can watch for and quickly treat any reaction. Resuscitation equipment and adrenaline are kept ready. You are only allowed home once the team is satisfied you are safe.
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, which makes a serious reaction more likely and more dangerous.
- You have a significant heart condition, or take medicines such as beta-blockers, that would make treating a reaction harder.
- Your allergy is mild and well controlled by avoidance and medicines, so the risks outweigh the likely benefit.
- You cannot commit to attending the clinic regularly over about three years.
- You are unable to recognise or respond to the warning signs of a reaction, or cannot stay for monitoring.
Delay or rearrange if…
- Your asthma is currently flaring or poorly controlled.
- You are unwell with a fever or chest infection on the day of an injection.
- You are pregnant or might become pregnant — a new course is not usually started in pregnancy.
- Your medicines, such as beta-blockers or ACE inhibitors, have not yet been reviewed.
- You had a significant reaction to your last injection that has not been assessed.
Alternatives to discuss
- Allergen avoidance measures, which are first-line for house dust mite and pet allergy.
- Regular antihistamines and steroid nasal sprays for hay fever symptoms.
- Sublingual (under-the-tongue) immunotherapy for suitable allergens such as grass pollen or dust mite.
- For insect venom, carrying an adrenaline auto-injector and avoidance if immunotherapy is not chosen.
- No immunotherapy, if symptoms are mild or the risks are too high for you.
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 symptoms and the need for antihistamines and steroid sprays in severe pollen allergy
- For bee and wasp venom allergy, can greatly lower the risk of a serious reaction to a future sting
- May improve quality of life when an allergy has been limiting work, sleep or daily activities
- Is the only treatment that changes the underlying allergy rather than just controlling symptoms
- Benefits can last for some years after a full course is completed
Risks & complications
- Redness, itching or swelling at the injection site
- Tiredness or mild flu-like feelings after an injection
- Worsening of usual allergy symptoms, such as a runny nose or itchy eyes, for a short time
- The need to attend the clinic frequently over a long period
- A larger local swelling that needs antihistamines or a slower dose increase
- Wheeze or chest tightness, especially in people with asthma
- Hives (urticaria) or more widespread itching after an injection
- Anaphylaxis — a severe, whole-body allergic reaction that needs immediate emergency treatment with adrenaline
- A reaction severe enough to require the course to be stopped
The most important risk is a severe allergic reaction (anaphylaxis), which is why every injection is given in a clinic with a waiting period and emergency treatment available. The risk is higher during the build-up phase, with rapid dose increases, and in people with poorly controlled asthma. Ask how the clinic monitors you, what they do if you react, and whether your asthma is well enough controlled to start.
Published figures to discuss
Reaction rates vary with the allergen, the dose schedule, how fast the dose is increased, and whether asthma is well controlled. Most reactions are mild and local; serious whole-body reactions are uncommon but are the reason injections are always given under supervision. Exact figures differ between clinics and extracts, so the ranges below are broad.
| Figure | Reported range | How to interpret it | Source / confidence |
|---|---|---|---|
| Local reaction at the injection site | Common | Redness, itching or swelling at the injection site is the most frequent side effect and is usually mild and short-lived. | Guide sourcesClinical context |
| Systemic (whole-body) reaction during venom immunotherapy build-up | Reported in roughly 8 to 20 in 100 people in large studies, with fewer when strict criteria are used | Most are mild to moderate and treatable. Risk is highest in the build-up phase and with bee venom or rapid schedules. Rates differ by allergen and protocol. | NHS — Allergies: treatmentnhs.ukSource-linked context |
| Anaphylaxis needing adrenaline | Rare, but important | This is the reason every injection is given in a clinic with a monitoring period and emergency treatment ready. | 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 as such, but you must stay in the clinic to be watched after each injection, and the treatment itself is a long commitment over about three years.
- Redness, itching or a small swelling at the injection site
- Feeling tired or mildly flu-like for a few hours after an injection
- A short-lived flare of your usual allergy symptoms
- Slow, gradual improvement in symptoms over months rather than days
Aftercare
- Stay in the clinic for the full monitoring period after every injection.
- Avoid vigorous exercise, hot baths and alcohol for a few hours after an injection.
- Use a cool compress and, if advised, an antihistamine for local swelling at the injection site.
- Keep your asthma medicines up to date and take them as prescribed.
- Carry any adrenaline auto-injector you have been prescribed and know how to use it.
- Attend all your appointments — missing doses can mean the dose has to be reduced and built up again.
- Tell the clinic about any reaction to a previous injection before the next one is given.
- Allergy diagnosis confirmed by tests, not just assumed
- Asthma reviewed and well controlled before starting
- Medicines list checked, including beta-blockers and ACE inhibitors
- Time set aside for frequent early visits and an hour's wait each time
- Adrenaline auto-injector collected if prescribed, and you know how to use it
- Clinic contact number saved in case of a delayed reaction
Scars and how they heal
Injections leave only a tiny needle mark in the skin of the upper arm, which fades. A red, itchy or swollen patch at the injection site is common and usually settles within a day or two; it is not a scar.
⚠ Get urgent help if…
- Difficulty breathing, wheeze or a tight chest after an injection
- Swelling of the lips, tongue or throat, or trouble swallowing
- Widespread hives, flushing or severe itching
- Feeling faint, dizzy or collapsing
- A fast heartbeat with feeling unwell or anxious
- Any reaction that comes on after you have left the clinic
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 symptoms are noticeably better and you need less day-to-day medicine, or that a future insect sting is far less likely to cause a serious reaction. Improvement usually builds over months, not immediately. Even a successful course may reduce rather than completely remove symptoms, and the response varies from person to person. Your specialist will judge 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 over time and a small number may be offered further treatment. For venom allergy, protection is high but a small risk of reaction to a future sting can remain, especially after stopping.
Related tests, treatments or support
Allergen immunotherapy is used alongside, not instead of, allergen avoidance and your usual allergy medicines, especially in the early phase. If you are allergic to more than one thing, your specialist will decide whether one or more allergens can be treated and in what order.
Follow-up & long-term care
You are reviewed at the clinic at each visit and at intervals through the course. The specialist checks your symptoms, your asthma control, how you tolerated previous injections, and whether the dose or schedule needs adjusting. Towards the end of about three years they discuss whether to stop and what to expect afterwards.
- Regular maintenance injections, usually every few weeks, for about three years
- Ongoing review of asthma control throughout the course
- Keeping and replacing any prescribed adrenaline auto-injector before it expires
- Continued allergen avoidance and usual medicines alongside the injections
Repeat, follow-on and what comes next
- If you react to a dose, the dose may be reduced and built back up more slowly, lengthening treatment.
- If symptoms return after a completed course, a specialist may consider a further period of treatment.
- Some people do not respond well enough and the treatment is stopped or switched.
- Missed appointments can require the dose to be restarted at a lower level.
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 monitoring period in clinic after every injection, with adrenaline and resuscitation equipment ready.
- Clear written instructions on warning signs and what to do if a reaction starts after you leave.
- Regular review of symptoms, asthma control and tolerance of injections.
- A named contact at the clinic for problems between visits.
- An honest discussion at the end of the course about expected 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 clinic and consultant fees for assessment and ongoing review
- The cost of the allergen extract, which varies by allergen and supplier
- The number of visits, which is high during the build-up phase
- Nursing time and the monitoring period after each injection
- Allergy testing to confirm the diagnosis before starting
- 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 allergen extract and how long each course will run
- Whether the price covers the full multi-year course or is charged per visit
- Nursing and monitoring costs for the waiting period after each injection
- What happens, and what it costs, if you have a reaction and need treatment or a slower schedule
- The cancellation and missed-appointment policy
On the NHS? Allergen immunotherapy is available on the NHS through specialist allergy clinics when an allergy is 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 risk is a serious allergic reaction, and that this is why home injection is not allowed.
- Starting treatment without asthma being assessed and controlled first.
- Not discussing the three-year commitment and frequent early visits.
- Being led to expect a cure rather than a reduction in symptoms.
- No clear written plan for what to do if a reaction happens after leaving the clinic.
Marketing red flags
- Offering allergy injections to take home or self-administer.
- Promising a guaranteed cure or complete end to your allergy.
- Starting injections without confirming the allergy by proper testing.
- Downplaying the risk of a serious reaction or the need for monitoring.
- 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 immunotherapy really likely to help me?
- How much improvement can I realistically expect, and how will we know if it is working?
- What is the chance of a serious reaction for me, and how is it managed in this clinic?
- Is my asthma well enough controlled to start safely?
- How many visits will I need, and how long must I wait after each injection?
- 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
Can I have the injections at home?
Is it available on the NHS?
How long does the whole treatment take?
Will it cure my allergy?
Why can't I have it if my asthma is poorly controlled?
What happens if I miss appointments?
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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 — Immunotherapy for allergic rhinitis guideline BSACI — Find a clinic (specialist allergy services) NICE QS119 — Specialist assessment for venom immunotherapy
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: Under-the-tongue allergy treatment (sublingual immunotherapy) · Bee and wasp sting allergy testing and treatment · House dust mite allergy management · Pet (animal) allergy management · Anaphylaxis assessment and adrenaline pen training