When should I use my adrenaline autoinjector?

Use your adrenaline autoinjector at the first sign of anaphylaxis — do not wait to see if it gets worse. Signs include: difficulty breathing, throat tightening or swelling, hoarse voice, wheezing, severe drop in blood pressure, collapsing, or a combination of skin symptoms (hives, swelling, flushing) with any of the above. Inject into the outer mid-thigh through clothing if needed, then lie flat (or sit if breathing is difficult), and call 000. Always go to hospital afterwards — even if symptoms improve quickly — because reactions can return 1–8 hours later (biphasic reaction).

Why is adrenaline given in the thigh and not anywhere else?

The outer mid-thigh (vastus lateralis muscle) is the preferred injection site because it has excellent blood supply and provides faster and more reliable absorption of adrenaline than the deltoid (upper arm) or subcutaneous (under the skin) injection. Speed of absorption matters in anaphylaxis because minutes count. The autoinjector is designed to deliver the correct dose into this muscle — it should be held firmly against the outer thigh for approximately 3 seconds. Injecting through clothing is acceptable if removing clothing would cause delay.

What are the most common triggers for anaphylaxis in Australia?

Food is the most common trigger, particularly in children — peanuts, tree nuts (cashew, pistachio, walnut), cow's milk, egg, sesame, shellfish, fish, and wheat account for most food-induced anaphylaxis in Australia. In adults, medications are the most common cause — particularly beta-lactam antibiotics (penicillin, amoxicillin), NSAIDs, and contrast media. Insect venom is a major cause in Australia, with jack jumper ants particularly relevant in Tasmania and south-eastern Australia. Around 10–15% of anaphylaxis has no identifiable trigger after full workup (idiopathic anaphylaxis).

Do I always need to go to hospital after using an EpiPen?

Yes — always. Adrenaline autoinjectors are designed to treat anaphylaxis as a bridge to definitive emergency care, not to replace it. The reason is biphasic anaphylaxis: in approximately 1–20% of reactions, symptoms resolve after the initial treatment but return 1–8 hours later, sometimes more severely than the first episode. A minimum 4-hour observation period in hospital is required after any treated anaphylaxis. Longer observation is needed if the initial reaction was severe, if asthma is present, if there was a slow response to adrenaline, or if access to medical care after discharge would be limited.

What is an ASCIA Action Plan and do I need one?

An ASCIA Action Plan is a written emergency plan provided by an Australian allergist or GP to everyone diagnosed with anaphylaxis. It shows in plain language how to recognise a reaction, when to use the adrenaline autoinjector, how to position the person, and when to call 000. It is device-specific — separate plans exist for EpiPen, Anapen, Jext, and neffy intranasal adrenaline. The plan is usually printed on a red form and should be kept with the autoinjector at all times. Schools, childcare centres, and workplaces should have a copy. Annual review and update with your GP or allergist is recommended.

Anaphylaxis

Anaphylaxis: recognition, emergency treatment, and Australian prevention

By Dr HB Lo, FACRRM Reviewed 17 June 2026 10 min read

Anaphylaxis is a severe, life-threatening allergic reaction involving skin or mucous membranes, the respiratory tract, and the cardiovascular system. Per ASCIA 2024 guidelines, it is defined as acute onset with skin or mucosal features plus respiratory compromise or blood pressure drop, or two or more organ systems involved after allergen exposure.

Adrenaline injected into the outer mid-thigh is the only first-line treatment — antihistamines and steroids are adjunctive only and must never delay its use. Minimum 4-hour observation is required due to biphasic reaction risk. All patients need an adrenaline autoinjector prescription, a signed ASCIA Action Plan, and allergist referral.

What anaphylaxis is — and why minutes matter

Anaphylaxis is a severe, rapidly progressing allergic reaction that can cause death within minutes if untreated. It involves multiple organ systems simultaneously: skin and mucous membranes, the respiratory tract, the cardiovascular system, and the gut. The key phrase from ASCIA (Australasian Society of Clinical Immunology and Allergy) 2024 guidelines is “severe systemic hypersensitivity with rapid onset and risk of death.”

Australia sees approximately 10–20 deaths from anaphylaxis annually, despite adrenaline autoinjectors being widely available — most deaths are associated with delayed use of adrenaline. This is the central message: adrenaline is the only first-line treatment, and it must never be delayed. Antihistamines and steroids are supportive adjuncts, not substitutes.

The lifetime risk of anaphylaxis in Australia is approximately 1–3%.

A. Core clinical — the AU general-practice framework

Diagnosis: ASCIA 2024 criteria

ASCIA 2024 defines anaphylaxis as any one of:

Acute onset illness with skin or mucosal involvement (hives, flushing, swelling) plus at least one of: respiratory compromise (wheeze, stridor, breathlessness, hypoxia) or reduced blood pressure / end-organ dysfunction
Two or more of the following occurring together after likely allergen exposure: skin/mucosal symptoms; respiratory symptoms; reduced blood pressure; persistent gastrointestinal symptoms
Reduced blood pressure after exposure to a known allergen (below age-specific thresholds)

Skin and mucosal features (urticaria, angioedema, flushing, lip or tongue swelling) are present in 80–90% of cases. Importantly, anaphylaxis can occur without skin features in 10–20% of cases — particularly in drug-induced and exercise-induced reactions.

Common triggers in Australia

Food (~50% of anaphylaxis overall; predominant in children): peanuts, tree nuts (cashew, pistachio, walnut, almond), cow’s milk, egg, sesame, shellfish, fish, and wheat account for the vast majority of food-induced anaphylaxis. Cofactors — alcohol, NSAIDs, exercise within 4 hours of eating, and menstruation — can amplify or trigger reactions in previously tolerant individuals.

Medications (~20%; predominant in adults): beta-lactam antibiotics (penicillin, amoxicillin, cefalexin), NSAIDs, opioids, radiocontrast media, and perioperative anaesthetic agents (rocuronium, suxamethonium are leading causes in surgical anaphylaxis).

Insect venom (~15%): bees, wasps, and notably jack jumper ants (Myrmecia pilosula) in Tasmania and south-eastern Australia — an almost uniquely Australian cause of severe venom anaphylaxis; immunotherapy is available and highly effective.

Idiopathic (~10–15%): no identifiable trigger after full allergist workup.

Exercise-induced: particularly food-dependent exercise-induced anaphylaxis (FDEIA) — where eating a trigger food and then exercising produces anaphylaxis that neither trigger alone would cause.

Risk factors for severe or fatal anaphylaxis

Poorly controlled asthma (most important modifiable risk factor)
Delayed or absent adrenaline administration
Previous anaphylaxis (approximately 30% will have a recurrence in their lifetime)
Beta-blocker or ACE-inhibitor use (these impair the response to adrenaline and worsen severity)
Systemic mastocytosis (persistently elevated serum tryptase)
Remote location with delayed access to emergency care

Acute management — step by step

Per ASCIA 2024 guidelines, Australian Resuscitation Council guideline 9.2.7, and eTG:

Step 1 — Recognise and remove the trigger (stop drug infusion, remove insect sting).

Step 2 — Position correctly:

Lay flat (supine) if blood pressure is reduced or circulation is compromised
Sitting upright if respiratory distress predominates
Never stand a hypotensive patient — fatal postural collapse is documented
Pregnant: left lateral tilt to relieve aortocaval compression

Step 3 — Adrenaline IM into the outer mid-thigh (the cornerstone — DO NOT delay):

Dose: 0.01 mg/kg of 1:1,000 (= 1 mg/mL) adrenaline, intramuscular injection into the vastus lateralis
Maximum dose: 0.5 mg per injection
Standard adult dose: 0.5 mg (0.5 mL of 1:1,000) IM
Paediatric: 0.15 mg under 15 kg; 0.3 mg for 15–50 kg; 0.5 mg over 50 kg
Repeat every 5 minutes if symptoms persist or worsen
Autoinjectors (EpiPen, Anapen, Jext, neffy) are designed for patient and bystander use; ampoule and syringe offer precise paediatric dosing in a clinical setting

Step 4 — Ancillary measures:

High-flow oxygen (8–10 L/min via face mask) — target SpO₂ ≥94%
IV access × 2 large-bore
IV fluid bolus 20 mL/kg crystalloid (0.9% saline or Hartmann’s) for hypotension
Salbutamol 4–6 puffs via spacer or continuous nebulised for bronchospasm
Category 1 transfer to emergency department with pre-notification (ISBAR handover)

Step 5 — Refractory anaphylaxis (failed response to 3 or more IM doses):

IV adrenaline infusion 0.05–0.5 µg/kg/min — only in a monitored setting with cardiac monitoring and experienced personnel
Glucagon 1–5 mg IV bolus for patients on beta-blockers (beta-blockade impairs the response to adrenaline; glucagon bypasses this)
Vasopressin for refractory hypotension in specialist hands

Step 6 — Adjunctive measures (NEVER first-line):

Antihistamines (oral cetirizine or parenteral promethazine) — for urticaria and pruritus only; do not delay or replace adrenaline
Corticosteroids — the historical practice of giving steroids to prevent biphasic reactions has weak supporting evidence per ASCIA 2024 guidelines; reasonable in protracted reactions but should never delay adrenaline or transfer

Step 7 — Observation:

Minimum 4 hours after resolution of symptoms — for biphasic reaction risk (occurs in 1–20% of anaphylaxis cases, typically within 4–8 hours)
Longer observation for severe initial reaction, slow response to adrenaline, persistent symptoms, comorbid asthma, beta-blocker use, or remote location after discharge

B. Biphasic reactions and evidence controversies

Biphasic anaphylaxis

Biphasic reaction — recurrence of anaphylaxis 1–8 hours after the initial resolution — occurs in approximately 1–20% of cases. It can be more severe than the first episode. This unpredictable recurrence is the reason minimum 4-hour observation is mandatory after any anaphylaxis requiring adrenaline treatment. The timing and predictors of biphasic reactions are incompletely understood, which is why the observation period cannot be shortened based on initial presentation severity.

Steroid controversy

Corticosteroids are traditionally given in anaphylaxis to prevent biphasic reactions. However, ASCIA 2024 guidelines note that recent evidence questions their efficacy for biphasic prevention. Steroids may be reasonable in protracted reactions or severe initial presentations, but they add nothing to the first-line management — adrenaline does.

Intranasal adrenaline (neffy)

Neffy (intranasal adrenaline) received TGA approval in 2026 as an alternative to needle-based autoinjectors for people with significant needle phobia or other access barriers. PBS listing is expanding. Evidence is sufficient to support its use as a reasonable alternative; however, it is newer, accumulated real-world experience is still growing, and mucosal oedema during anaphylaxis may theoretically affect absorption. An established autoinjector remains the standard first choice.

Allergen immunotherapy

For insect venom anaphylaxis — particularly bee and jack jumper ant — subcutaneous venom immunotherapy (VIT) is highly effective and PBS-listed under Authority Required for confirmed venom allergy with IgE evidence. After a full course, most adults achieve long-term protection. Oral immunotherapy for food allergy (peanut, milk, egg) is available at select Australian specialist centres; it remains in the early adoption phase and is done under specialist supervision.

C. ASCIA Action Plans and autoinjectors

ASCIA Action Plans 2026

ASCIA Action Plans are the cornerstone of anaphylaxis self-management in Australia. They come in 5 versions — a general plan and device-specific plans for EpiPen, Anapen, Jext, and neffy intranasal. Each plan is a printed red form, completed and signed by the prescribing GP or allergist. The plan shows:

How to recognise mild-to-moderate allergic reaction versus anaphylaxis
When to use the autoinjector
The correct technique (written and illustrated)
When to call 000
Post-reaction instructions including lying flat and hospital attendance

Action Plans should be kept with the autoinjector at all times — at home, school, work, and in transit. Schools and childcare centres in Australia are required to have an ASCIA Action Plan for any enrolled child with a history of anaphylaxis.

Adrenaline autoinjectors — Australian prescribing

All major autoinjectors are PBS-listed in Australia under Authority Required for confirmed anaphylaxis:

EpiPen (0.15 mg junior, 0.3 mg, 0.5 mg) — the most commonly prescribed
Anapen (0.15 mg, 0.3 mg, 0.5 mg) — alternative; same indications
Jext (0.15 mg, 0.3 mg) — PBS-listed
neffy (intranasal adrenaline) — TGA-approved 2026; PBS listing expanding for needle-averse patients

Consider prescribing two autoinjectors for: patients with a history of severe anaphylaxis, those in remote locations, those who divide time between school/work and home, or patients of large body habitus where a second dose is more likely to be needed.

Autoinjectors have expiry dates and temperature sensitivity — annual review and replacement are part of ongoing GP follow-up.

D. Australian operations

MBS billing

The anaphylaxis consultation — particularly the post-event review and discharge planning appointment involving autoinjector prescription, ASCIA Action Plan completion, trigger identification counselling, and education — typically warrants MBS item 36 (Level C) or item 44 (Level D). Specific IgE pathology testing (skin prick test by allergist, RAST/ImmunoCAP) is MBS-rebatable. Serum tryptase is rebatable via standard pathology.

Post-anaphylaxis anxiety is common and can be debilitating; a Mental Health Care Plan (MBS item 2715) opens access to 10 subsidised psychology sessions for post-event anxiety management.

PBS — adrenaline autoinjectors

All autoinjectors listed above are PBS Authority Required for confirmed anaphylaxis. Adrenaline ampoules (1:1,000, 1 mg/mL) for GP doctor’s bag stocking are available on PBS general. Allergen-specific immunotherapy for venom is PBS Authority Required after allergist confirmation with IgE evidence.

Schools, workplaces, and childcare

Australian schools and childcare centres are required to have an ASCIA Action Plan, a stored autoinjector, and trained staff for any child with diagnosed anaphylaxis. Resources and pro forma are available directly from Allergy & Anaphylaxis Australia. Employers have obligations under occupational health and safety law to have an emergency management plan that includes provision for anaphylaxis where workers have known allergy.

Mandatory reporting

Severe anaphylaxis suspected to be drug-induced should be reported to the TGA Adverse Drug Reaction reporting system (Blue Card or online). Death from anaphylaxis is a reportable death to the relevant State Coroner.

E. Special populations

Children. Food allergy anaphylaxis is predominantly a paediatric presentation. Parents and carers, as well as schools, require comprehensive education including autoinjector technique training with a practice device. Allergen immunotherapy for food allergy (oral immunotherapy) is available in specialist paediatric allergy centres. Royal Children’s Hospital Melbourne clinical practice guideline provides paediatric-specific management detail.

Adults with newly diagnosed anaphylaxis. Insect venom and medication-induced anaphylaxis predominate in adult presentations. Beta-blocker and ACE-inhibitor use worsens anaphylaxis severity and impairs the response to adrenaline — this is reviewed in consultation with the prescribing physician when present.

Patients with asthma. Asthma — particularly poorly controlled asthma — is the most important risk factor for fatal anaphylaxis. Anaphylaxis and acute asthma can co-exist: treat both. Optimisation of asthma management is a priority in the follow-up plan.

Patients on beta-blockers or ACE-inhibitors. These medications impair the cardiovascular response to adrenaline (beta-blockers) or potentiate anaphylaxis severity via bradykinin pathways (ACE-inhibitors). Carry glucagon for beta-blocker patients as a backup for adrenaline-refractory anaphylaxis. A medication review with the relevant prescriber is appropriate following confirmed anaphylaxis.

Pregnancy. Anaphylaxis in pregnancy requires IM adrenaline — the risk to the foetus from untreated maternal anaphylaxis far exceeds any theoretical risk from adrenaline. Left lateral positioning for aortocaval decompression is used alongside standard management. Urgent obstetric involvement alongside emergency care is appropriate.

Indigenous Australians. Coordinate with ACCHOs where appropriate; ensure culturally safe education and Closing the Gap PBS Co-payment provisions for autoinjectors and ongoing therapy are accessed.

When to escalate

Call 000 and transfer to emergency department immediately for any confirmed or suspected anaphylaxis. In the GP or urgent-care setting:

Every anaphylaxis treated with adrenaline — Category 1 emergency department transfer for minimum 4-hour observation
Refractory anaphylaxis — failing ≥3 IM adrenaline doses — requires ICU and IV adrenaline infusion in a fully monitored setting
Anaphylaxis in pregnancy — urgent obstetric review alongside emergency management
Cardiac arrest from anaphylaxis — advanced life support; glucagon for known beta-blocker use; ECMO considered in specialist centres for refractory cardiac arrest
Post-event: all patients — allergist or immunologist referral for trigger identification, IgE testing, tryptase measurement, and consideration of allergen immunotherapy

What this article is and is not

This is general health information drawn from current Australian guidelines — ASCIA 2024 Acute Management guidelines, Australian Resuscitation Council guideline 9.2.7, Therapeutic Guidelines (eTG), and Australian Medicines Handbook. It is not personal medical advice and does not create a doctor–patient relationship. Anaphylaxis is a medical emergency — if you think you are experiencing anaphylaxis, inject adrenaline and call 000 immediately. Do not delay while reading information.

For ongoing support and resources: Allergy & Anaphylaxis Australia, ASCIA patient information, HealthDirect — Anaphylaxis, MedicAlert Australia.

Emergency: call 000.

Sources cited

Frequently asked questions

When should I use my adrenaline autoinjector?

Use your adrenaline autoinjector at the first sign of anaphylaxis — do not wait to see if it gets worse. Signs include: difficulty breathing, throat tightening or swelling, hoarse voice, wheezing, severe drop in blood pressure, collapsing, or a combination of skin symptoms (hives, swelling, flushing) with any of the above. Inject into the outer mid-thigh through clothing if needed, then lie flat (or sit if breathing is difficult), and call 000. Always go to hospital afterwards — even if symptoms improve quickly — because reactions can return 1–8 hours later (biphasic reaction).
Why is adrenaline given in the thigh and not anywhere else?

The outer mid-thigh (vastus lateralis muscle) is the preferred injection site because it has excellent blood supply and provides faster and more reliable absorption of adrenaline than the deltoid (upper arm) or subcutaneous (under the skin) injection. Speed of absorption matters in anaphylaxis because minutes count. The autoinjector is designed to deliver the correct dose into this muscle — it should be held firmly against the outer thigh for approximately 3 seconds. Injecting through clothing is acceptable if removing clothing would cause delay.
What are the most common triggers for anaphylaxis in Australia?

Food is the most common trigger, particularly in children — peanuts, tree nuts (cashew, pistachio, walnut), cow's milk, egg, sesame, shellfish, fish, and wheat account for most food-induced anaphylaxis in Australia. In adults, medications are the most common cause — particularly beta-lactam antibiotics (penicillin, amoxicillin), NSAIDs, and contrast media. Insect venom is a major cause in Australia, with jack jumper ants particularly relevant in Tasmania and south-eastern Australia. Around 10–15% of anaphylaxis has no identifiable trigger after full workup (idiopathic anaphylaxis).
Do I always need to go to hospital after using an EpiPen?

Yes — always. Adrenaline autoinjectors are designed to treat anaphylaxis as a bridge to definitive emergency care, not to replace it. The reason is biphasic anaphylaxis: in approximately 1–20% of reactions, symptoms resolve after the initial treatment but return 1–8 hours later, sometimes more severely than the first episode. A minimum 4-hour observation period in hospital is required after any treated anaphylaxis. Longer observation is needed if the initial reaction was severe, if asthma is present, if there was a slow response to adrenaline, or if access to medical care after discharge would be limited.
What is an ASCIA Action Plan and do I need one?

An ASCIA Action Plan is a written emergency plan provided by an Australian allergist or GP to everyone diagnosed with anaphylaxis. It shows in plain language how to recognise a reaction, when to use the adrenaline autoinjector, how to position the person, and when to call 000. It is device-specific — separate plans exist for EpiPen, Anapen, Jext, and neffy intranasal adrenaline. The plan is usually printed on a red form and should be kept with the autoinjector at all times. Schools, childcare centres, and workplaces should have a copy. Annual review and update with your GP or allergist is recommended.

Source quality

Sources grouped by evidence tier. AU primary tier first; international where AU is silent or lagging; named-author reconstruction where guidelines have not yet caught up. How tiers work.

T1 AU primary 12 sources