Signs of anaphylaxis

Anaphylaxis causes respiratory and/or cardiovascular signs or symptoms AND involves other organ systems, such as the skin or gastrointestinal tract, with:

  • signs of airway obstruction, such as cough, wheeze, hoarseness, stridor or signs of respiratory distress (eg tachypnoea, cyanosis, rib recession)
  • upper airway swelling (lip, tongue, throat, uvula or larynx)
  • tachycardia, weak/absent carotid pulse
  • hypotension that is sustained and with no improvement without specific treatment (Note: in infants and young children limpness and pallor are signs of hypotension)
  • loss of consciousness with no improvement once supine or in head-down position
  • skin signs, such as pruritus (itchiness), generalised erythema (redness), urticaria (weals) or angioedema (localised or general swelling of the deeper layers of the skin or subcutaneous tissue)
  • abdominal cramps, diarrhoea, nausea and/or vomiting
  • sense of severe anxiety and distress

Managing anaphylaxis
  • If the person is unconscious, lie them on their left side and position to keep the airway clear. If the person is conscious, lie supine in ‘head-down and feet-up’ position (unless this causes breathing difficulties).
  • Give adrenaline by intramuscular injection (see below for dosage) if there are any signs of anaphylaxis with respiratory and/or cardiovascular symptoms or signs. Although adrenaline is not required for generalised non-anaphylactic reactions (such as skin rash without other signs or symptoms), administration of intramuscular adrenaline is safe.
  • Call for assistance. Never leave the patient alone.
  • If oxygen is available, administer by facemask at a high flow rate.
  • If the person does not improve within 5 minutes, repeat doses of adrenaline every 5 minutes until they improve.
  • Check breathing; if absent, commence basic life support or appropriate cardiopulmonary resuscitation (CPR) as per the Australian Resuscitation Council guideline.
  • Transfer all cases to hospital for further observation and treatment.
  • Fully document the event, including the time and dose(s) of adrenaline given.

Experienced practitioners may choose to use an oral airway, if the appropriate size is available, but its use is not routinely recommended, unless the patient is unconscious.

Antihistamines and/or hydrocortisone are not recommended for the emergency management of anaphylaxis.

Adrenaline dosage

The recommended dose of 1:1000 adrenaline is 0.01 mL/kg body weight (equivalent to 0.01 mg/kg), up to a maximum of 0.5 mL or 0.5 mg, given by deep intramuscular injection into the anterolateral thigh. Do not administer adrenaline 1:1000 intravenously.

1:1000 adrenaline is recommended because it is universally available. It contains 1 mg of adrenaline per mL of solution in a 1 mL glass vial. Use a 1 mL syringe to improve measurement accuracy when drawing up small doses.

The following table lists the doses of 1:1000 adrenaline to be used if the exact weight of the person is not known (based on the person’s age).

Doses of 1:1000 adrenaline:
~ <1 year (<7.5 kg) 0.10 mL
~ 1–2 years (10 kg) 0.10 mL
~ 2–3 years (15 kg) 0.15 mL
~ 4–6 years (20 kg) 0.20 mL
~ 7–10 years (30 kg) 0.30 mL
~ 10–12 years (40 kg) 0.40 mL
>12 years and adults, including pregnant women (over 50 kg)

0.50 mL

Source: Modified from Australasian Society of Clinical Immunology and Allergy (ASCIA). Guidelines: acute management of anaphylaxis. Sydney: ASCIA; 2017.

Last updated: 
8 March 2022
Last reviewed: 
8 March 2022

Definitions

ASCIA
Australasian Society of Clinical Immunology and Allergy