Anaphylaxis is a serious, life-threatening allergic reaction. Features include airway compromise, breathing or circulation difficulties and skin changes. Skin changes alone are not a sign of anaphylaxis but are present in 80% of patients with anaphylaxis.

Signs & Symptoms

  • Airway – feeling their throast closing up, stridor (inspiratory sound) & hoarse voice
  • Breathing – shortness of breath, increased respiratory rate, wheeze, cyanosis
  • Circulation – pale, clammy, hypotensive, tachycardic, sense of impending doom or drowsy/collapse
  • Skin – erythema, urticaria, angioedema (usually affecting eyelids and lips)

Differential includes ACE inhibitor-induced angioedema, asthma, panic attack, vasovagal syncope. In the two latter differentials, the absence of skin, swelling and breathing difficulties can help differentiate.

Emergency Management

Follow the ALS guidelines

  • Stop the agent causing the reaction & call for help (ensure anaesthetic support) 
  • Establish airway & give high flow oxygen
  • Administer IM adrenaline
    • Adults – 0.5ml of 1 in 1000 adrenaline IM (500 micrograms)
    • Children 
      • Over 12 years – dose as above
      • 6-12 years – 0.3ml of 1 in 1000 adrenaline IM (300 micrograms)
      • Under 6 years – 0.15ml of 1 in 1000 adrenaline IM (150 micrograms)
    • Can be repeated after 5 minutes
  • Fluid bolus (crystalloid only- stop colloids as they may cause anaphylaxis)
    • Adults – 500ml to 1000ml crystalloid
    • Children – 10mL/kg

Antihistamines are no longer recommended for the treatment of anaphylaxis as they delay emergency management. Antihistamines (e.g. cetirizine) can be effective for the cutaneous features.

Also, corticosteroids (e.g. hydrocortisone 200mg) is no longer recommended, except in refractory reactions, ongoing asthma or resistant shock.

Refractory anaphylaxis may be managed with further IV fluids and IM adrenaline every 5 minutes until an infusion of adrenaline is started.

Further Management

  • Ensure you document the time of onset of the anaphylaxis
  • Document the preceding circumstances. Ask the patient/NOK to note down everything eaten that day, new medications or any other changes as they will forget very quickly (and it’ll be necessary to identify the trigger).
  • Mast Cell Tryptase is recommended (U&Es bottle, ensure time is recorded)
    • Sample 1 – as soon as feasible after resuscitation is started
    • Sample 2 – within 2h (but no later than 4h) from onset of symptoms
    • Sample 3 – at 24h or later following recovery for baseline
  • Refer the patient (if appropriate) to allergy services
  • Ensure they don’t leave until they’re comfortable taking an adrenaline pen & that they know they must call an ambulance regardless after they take it
  • Provide information on avoiding triggers, signs of anaphylaxis, observing for biphasic reactions and information of follow up
  • Monitor the patient for at least 12h
  • Make sure to register the suspected agent as an allergy

References & Reading

Written by Dr Keryn Hall FY2
Edits by Dr Akash Doshi ST4 – updated in Nov 2021

How useful was this post?

Click on a star to rate it!

Average rating 5 / 5. Vote count: 8

No votes so far! Be the first to rate this post.

As you found this post useful...

Follow us on social media!

We are sorry that this post was not useful for you!

Let us improve this post!

Tell us how we can improve this post?

2 thoughts on “Anaphylaxis”

  1. Just a little note- the Resus Council guidelines changed this year (2021) and IV hydrocortisone and chlorphenamine is no longer recommended.

Leave a Comment

Your email address will not be published.

Follow us

Our Newsletter

Trending Now

Bradyarrhythmias are abnormal heart rhythms with a pulse rate of <60 beats per minute (bpm). This...
Management of low blood sugar in conscious & unconscious patients, finding common causes, adjusting medications...
Serum calcium concentration is tightly regulated between 2.1-2.6mmol/L. Severe hypercalcaemia is a life-threatening...
Reporting Adverse Drug Reactions
The World Health Organization (WHO) defines adverse drug reactions (ADR) as “any response to a drug which...
Junior Doctor Pay Calculator
We’ve created a junior doctor pay calculator which will help you better understand your salary,...
PICC Lines and Midlines
You may well be asked to take blood from a PICC line or be called to see a patient because their PICC...
Safeguarding History – The Basics
Children are vulnerable. Unfortunately, child abuse does happen, and it has a significant and lifelong...
Scroll to Top

Sign up for our awesome resources

Free webinars every week, referral cheat sheet & other amazing content!