Allergic reaction and anaphylaxis treatment (Acute management of allergic reaction and anaphylaxis)
Emergency and same-day care for an allergic reaction, from antihistamines for a mild reaction to adrenaline for anaphylaxis, which is a life-threatening 999 emergency.
✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review
In short
- Anaphylaxis is a 999 emergency. If someone has an auto-injector and signs of a severe reaction, use the adrenaline first, then call 999 and say the word 'anaphylaxis'.
- Do not drive to a clinic during a serious reaction, and do not stand or walk around even if you feel better — lie down with your legs raised.
- If there is no improvement after 5 minutes, a second adrenaline dose can be given in the other thigh. Everyone who has had adrenaline still needs hospital, because symptoms can return.
- A private allergy clinic is for working out your triggers and prevention plan afterwards — it cannot replace emergency 999/A&E care.
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.
Adrenaline can rapidly reverse the life-threatening parts of anaphylaxis — opening the airways and supporting blood pressure.
Going to a clinic (NHS or private) during an active severe reaction — that is always 999/A&E, not an appointment.
Adrenaline given, 999 called, lying down with legs raised. The most dangerous time is the first few minutes — speed matters.
A written, personalised anaphylaxis action plan stating exactly when to use adrenaline and call 999.
Adrenaline given, 999 called, lying down with legs raised. The most dangerous time is the first few minutes —...
Observation in A&E. The team watches breathing, blood pressure and whether symptoms return. You may be given...
A reaction can occasionally come back. Stay near help, avoid the trigger, and don't be alone if you can avoid it...
You should be referred to an allergy clinic to confirm the trigger, get a written plan and renew training on your...
What is treatment for an allergic reaction and anaphylaxis?
An allergic reaction is your body over-reacting to something that is usually harmless, such as a food, a medicine, latex, or an insect sting. Most reactions are mild — an itchy rash, hives, a runny nose or some swelling — and settle with an antihistamine and avoiding the trigger.
Anaphylaxis is a severe, whole-body allergic reaction that comes on fast and can be life-threatening. It needs adrenaline straight away and a 999 call. The key danger signs are trouble breathing (wheeze, noisy breathing, a tight throat or hoarse voice), swelling of the tongue or throat, feeling faint, dizzy or floppy, or skin that turns pale, blue or grey. Children can also become very drowsy or limp.
This guide explains what to do in the moment and how the NHS treats a reaction. It is not a substitute for proper training on your own auto-injector. If you carry adrenaline, learn how and when to use it, and replace it before it expires.
A private allergy clinic can be excellent for finding out what you react to and how to avoid it after the event. It is not the place to go while a serious reaction is happening — that is always 999 and A&E.
Types, options & approaches
There may be different ways to do this. The right approach depends on the clinical question and your circumstances.
Mild reaction vs anaphylaxis
| Mild reaction | Anaphylaxis | |
|---|---|---|
| Breathing | Normal | Wheeze, noisy or fast breathing, tight throat |
| Throat/tongue | Not affected | Swelling, hoarse voice, trouble swallowing |
| How you feel | Itchy, blotchy, uncomfortable | Faint, dizzy, floppy, collapsing |
| First action | Antihistamine, avoid trigger | Adrenaline now, then call 999 |
| Where | Home or pharmacist | 999 and hospital, every time |
If you are ever unsure whether it is mild or severe, treat it as the more serious one. Adrenaline is safe to give if in doubt.
Preparing for your treatment
- If you have a known serious allergy, always carry two in-date adrenaline auto-injectors, not one — a second dose is sometimes needed.
- Learn how to use your specific device; the technique differs between EpiPen, Jext and Emerade. Practise with a trainer pen.
- Make sure family, friends, school or workplace know where your pens are and how to use them.
- Check the expiry date regularly and reorder before it runs out; sign up for the manufacturer's expiry-alert service.
- Keep a written allergy action plan (your GP or allergy clinic can provide one) and wear medical-alert jewellery if advised.
- Know your triggers and read food labels carefully; tell restaurants about your allergy before ordering.
What happens
If anaphylaxis is suspected, the adrenaline auto-injector is used straight away into the outer thigh (it works through clothing). Adrenaline is the first and most important treatment — antihistamines and inhalers are not enough on their own.
After giving adrenaline, call 999 and say clearly that it is 'anaphylaxis' so the call is prioritised. The person should lie down with their legs raised to help blood flow; if they are struggling to breathe they can be propped up, and a pregnant person should lie on their left side. They must not stand up or walk, even if they feel better, because that can cause a sudden, dangerous drop in blood pressure.
If there is no improvement after about 5 minutes, a second auto-injector is given in the other thigh. Stay with the person until the ambulance arrives.
In hospital, the team continues adrenaline if needed, gives oxygen and fluids into a vein, and keeps the person under observation because the reaction can come back. How long that observation lasts is judged case by case, based on how severe the reaction was and how quickly it responded. If someone recovered fast and fully after a single dose of adrenaline, they may be able to go home after as little as 2 hours — but only if they have two adrenaline auto-injectors, they and their family have been shown how to use them, and there is someone able to watch over them. Observation is usually at least 6 hours if two doses of adrenaline were needed, or the person has had a reaction that came back before. It is usually at least 12 hours if more than two doses were needed, there was severe breathing difficulty, the trigger is still being absorbed, the reaction happened late at night, the person would struggle to get help quickly if they got worse, or emergency care is hard to reach. Everyone goes home with an emergency plan and a referral.
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…
- Going to a clinic (NHS or private) during an active severe reaction — that is always 999/A&E, not an appointment.
- Relying on antihistamines or an asthma inhaler alone to treat anaphylaxis.
- Managing a confirmed severe allergy without carrying in-date adrenaline.
- Self-diagnosing your trigger without proper allergy testing, which can lead to unnecessary avoidance or false reassurance.
Delay or rearrange if…
- This is about prevention, not the emergency: never delay adrenaline or a 999 call in a reaction that is happening.
- Allergy testing can be less reliable soon after a reaction or while on antihistamines — your clinician will advise timing.
- Skin testing may be deferred if your skin is very inflamed (for example with eczema flares).
- Some tests are interpreted differently in pregnancy or with certain medicines — tell your clinician.
Alternatives to discuss
- NHS allergy clinic referral through your GP after a reaction.
- Strict trigger avoidance and label-reading as the foundation of management.
- Venom immunotherapy for proven insect-sting allergy in selected people.
- Oral immunotherapy for some food allergies in specialist centres.
- A clear written action plan and auto-injector training for everyone around 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
- Adrenaline can rapidly reverse the life-threatening parts of anaphylaxis — opening the airways and supporting blood pressure.
- Acting fast saves lives; the biggest risk in anaphylaxis is delaying adrenaline.
- Hospital observation catches a reaction that returns hours later before it becomes dangerous.
- A clear written action plan helps you and those around you respond confidently next time.
- Referral afterwards can confirm your trigger and reduce the chance of another reaction.
Risks & complications
- After adrenaline: a fast or pounding heartbeat, tremor, pale skin, headache and feeling anxious — these are expected and pass.
- Antihistamines can cause drowsiness (the older types) — use non-drowsy ones where possible.
- Soreness or a small bruise at the injection site.
- The reaction returning hours after it first settled (a biphasic reaction), which is why hospital observation matters.
- Accidentally injecting a thumb or finger instead of the thigh, which needs medical review.
- Needing more than two doses of adrenaline before the ambulance arrives.
- Serious heart rhythm problems from adrenaline, mainly a concern in people with significant heart disease — but the risk of untreated anaphylaxis is far greater.
- Death from anaphylaxis, which is rare but is more likely when adrenaline is delayed or not given.
The most important message is that the risks of withholding adrenaline are much greater than the risks of giving it. If someone has signs of a severe reaction and an auto-injector is available, use it. The main thing to ask your allergy clinician is exactly which symptoms should trigger your pen, and how to recognise a reaction that is coming back.
Published figures to discuss
Anaphylaxis is uncommon and deaths are rare, but reliable, precise rates are hard to quote because reactions vary hugely by trigger, dose, how quickly adrenaline is given, and the person's other conditions (such as asthma). We give cautious figures and avoid implying any reaction is predictable.
| Figure | Reported range | How to interpret it | Source / confidence |
|---|---|---|---|
| Fatal outcome from anaphylaxis | Rare — UK data suggest roughly 20–30 anaphylaxis deaths a year | Risk is higher when adrenaline is delayed or not given, and in people with poorly controlled asthma. | NHS — Anaphylaxisnhs.ukSource-linked context |
| Reaction returning hours later (biphasic) | Around 4–6% in modern reviews, with wide study ranges roughly 1–20% | More likely after severe reactions, delayed adrenaline, hypotension or needing more than one adrenaline dose; observation time should follow NICE/RCUK guidance. | NICE CKS — Angio-oedema and anaphylaxiscks.nice.org.ukPublished figure |
| Need for a second adrenaline dose | A minority of anaphylaxis reactions | If symptoms are not improving after 5 minutes, UK guidance advises giving a second adrenaline auto-injector, which is why carrying two matters. | Guide sourcesClinical context |
| Antihistamines delaying adrenaline | Recognised preventable safety risk | Antihistamines may help itch or hives but do not treat airway swelling, breathing difficulty or low blood pressure. | NHS — Anaphylaxisnhs.ukSource-linked 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
After a mild reaction you usually feel back to normal within hours. After anaphylaxis you will be tired and shaky for a day or two, and you must avoid the trigger and replace your used auto-injectors before doing anything risky.
- Feeling shaky, tired or anxious for a day or so after adrenaline and a frightening reaction.
- A racing heart and trembling for a short time straight after the injection.
- Lingering mild rash or itch that settles with antihistamines.
- A sore thigh where the auto-injector was used.
Aftercare
- Replace any used or expired auto-injectors straight away so you are never without two in-date pens.
- Avoid the trigger completely until you have an allergy assessment and a clear plan.
- Take any antihistamines or steroids exactly as the hospital advised for the next few days.
- Do not be alone for the first day or two after anaphylaxis if you can avoid it, in case symptoms return.
- Tell your GP so a referral to an allergy clinic can be arranged.
- Update or get a written allergy action plan and make sure family, school or work know it.
- Save the right emergency numbers and know your nearest A&E.
- Two in-date adrenaline auto-injectors carried at all times
- Written allergy action plan to hand
- Trainer pen practised with family/carers
- Manufacturer expiry-alert reminder set up
- GP informed and allergy referral requested
- Medical-alert jewellery considered
- Nearest A&E and 999 process clear to everyone around you
⚠ Get urgent help if…
- Trouble breathing, wheezing, noisy breathing, or a tight throat or hoarse voice — call 999 and use adrenaline now.
- Swelling of the tongue, lips or throat, or trouble swallowing.
- Feeling faint, dizzy, floppy or collapsing.
- Skin, lips or tongue turning pale, blue or grey, or skin that feels cold.
- A child who becomes drowsy, limp or unresponsive.
- A reaction that returns after it seemed to settle — call 999 again.
- No improvement 5 minutes after the first auto-injector — give the second dose.
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
Given early, adrenaline usually reverses anaphylaxis quickly, and most people recover fully. A good outcome means the airway, breathing and blood pressure return to normal and stay stable through the observation period.
Treatment does not cure the underlying allergy. You will still react if you meet the trigger again, so the lasting benefit comes from identifying the trigger, avoiding it, and always carrying in-date adrenaline.
An auto-injector only helps if it is in date and with you. Adrenaline degrades over time and in heat, so check expiry dates, store pens correctly, and replace them before they run out. Your allergy and your action plan should be reviewed periodically, as triggers and needs can change — especially in growing children, where the dose may need updating.
Related tests, treatments or support
After the emergency, treatment is usually combined with an allergy clinic assessment, which may include skin-prick or blood (specific IgE) testing, a tryptase blood test taken around the time of the reaction, and sometimes supervised drug or food challenges. For insect-sting allergy, venom immunotherapy may be offered. These are separate, planned steps — not part of emergency care.
Follow-up & long-term care
Anyone treated for anaphylaxis should be referred to a specialist allergy service. Follow-up confirms the trigger where possible, provides a written emergency plan, renews auto-injector training, and arranges any further testing or immunotherapy. Your GP coordinates repeat prescriptions for your pens.
- Always carry two in-date adrenaline auto-injectors.
- Check expiry dates and replace pens before they run out.
- Store pens away from extreme heat or cold and out of direct sunlight.
- Re-practise your technique with a trainer pen regularly.
- Review your allergy plan with your clinician, especially for children as they grow.
Repeat, follow-on and what comes next
- After a reaction you may need repeat allergy testing if the first results are unclear.
- Auto-injector doses for children are adjusted as they grow.
- Action plans are reviewed and updated as triggers, medicines or circumstances change.
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 written, personalised anaphylaxis action plan stating exactly when to use adrenaline and call 999.
- Confirmation of your trigger and clear avoidance advice.
- Prescription for two in-date auto-injectors plus device training for you and your family.
- A named route back into the allergy service and a plan for review.
- Advice on hospital observation and recognising a reaction that returns.
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:
- Emergency anaphylaxis care is NHS 999/A&E and is not a private purchase — this guide does not put a price on saving a life.
- Private costs, where they apply, relate to allergy assessment afterwards: consultation length and seniority of the allergist.
- Type and number of tests (skin-prick, blood/specific IgE, tryptase, component testing).
- Whether supervised food or drug challenges are needed, which use clinic time and monitoring.
- Whether immunotherapy (for example venom desensitisation) is recommended, which is a long course.
- Follow-up appointments, written action plans and prescriptions for auto-injectors.
- What the allergy assessment appointment includes and how long it lasts.
- Which tests are planned and the fee for each.
- Whether any supervised challenge is needed and how it is monitored and priced.
- Cost of follow-up appointments and a written allergy action plan.
- Whether auto-injector prescriptions and training are included.
- What happens, and what it costs, if results are inconclusive and further testing is needed.
On the NHS? All emergency treatment for anaphylaxis is provided free by the NHS through 999 and A&E, and adrenaline auto-injectors are prescribed on the NHS. Private allergy clinics are used for faster assessment, testing and prevention planning after a reaction, not for treating an emergency.
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
- Being told antihistamines or an inhaler are enough for a severe reaction.
- No clear written instructions on exactly when to use adrenaline.
- Being prescribed only one auto-injector when two should be carried.
- No advice that hospital observation is needed even after the pen 'works'.
- Being encouraged to attend a clinic rather than call 999 during a reaction.
Marketing red flags
- Any private service implying you should come to them instead of calling 999 in an emergency.
- Claims that a test can 'cure' or permanently fix a food allergy.
- Unproven 'allergy tests' (such as hair analysis or IgG food-intolerance panels) sold as diagnosing serious allergy.
- Promising you can safely stop carrying adrenaline after treatment without specialist evidence.
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.
- Exactly which symptoms should make me use my adrenaline straight away?
- How do I use my specific device, and can my family practise with a trainer pen?
- How will I recognise a reaction that comes back hours later?
- What is my confirmed trigger, and how strictly do I need to avoid it?
- Should I be referred for testing, and would immunotherapy help my type of allergy?
- 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
Should I drive to a private clinic if I'm having a serious reaction?
Is it bad to use adrenaline if I'm not sure it's anaphylaxis?
Why do I still need hospital if the adrenaline worked?
Are antihistamines or my asthma inhaler enough for anaphylaxis?
Can a private allergy clinic help me?
How many auto-injectors should I carry?
Find a verified specialist for allergic reaction and anaphylaxis treatment
Every consultant is GMC-checked and independently reviewed. Search by postcode and distance, or switch to a map. Ordered by rating, relevance and recency — never by who pays.
No verified consultants list this procedure yet — browse the full directory.
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 — Anaphylaxis Anaphylaxis UK — What to do in an emergency Anaphylaxis UK — Adrenaline fact sheet NICE CKS — Angio-oedema and anaphylaxis NICE NG258 — Anaphylaxis: assessment and referral after emergency treatment Resuscitation Council UK — Emergency treatment of anaphylaxis NHS — Allergies overview NICE NG258 — Period of observation after anaphylaxis NICE NG258 — Information for the public
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: Anaphylaxis assessment and adrenaline pen training · Food allergy and anaphylaxis advice · Allergy consultation · Allergy testing and management · Bee and wasp sting allergy testing and treatment