Urgent considerations

See Differentials for more details

Life-threatening conditions associated with urticaria that mandate immediate intervention, hospitalisation, or prescription of rescue medication include anaphylaxis and airway obstruction.

Anaphylaxis

Anaphylaxis is a potentially life-threatening allergic reaction - look for life-threatening problems:[21][22][23][24]

  • Sudden onset of airway and/or breathing and/or circulation problems

  • Skin changes are often the first feature of allergic reactions and are present in >80% of patients with anaphylaxis.

    • A maculopapular-appearing eruption may occur initially before the development of clinically typical urticaria.

    • Skin changes without life-threatening airway/breathing/circulation problems are not anaphylaxis. Most patients who present with an acute onset maculopapular eruption in response to a drug, food or insect bite or sting, do not progress to anaphylaxis.​

If anaphylaxis is present:[21][22][24]

Call for help

Remove trigger if possible (e.g., stop any infusion)

Lie patient flat

Give intramuscular adrenaline

Establish airway

Give high flow oxygen

Apply monitoring: pulse oximetry, ECG, blood pressure

Repeat intramuscular adrenaline after 5 mins

Give intravenous fluid bolus

The comprehensive management of anaphylactic shock is beyond the scope of this topic and guidelines should be consulted for more detail.[21][22][23]​​[25]​​

Angio-oedema with airway compromise

Episodes of urticaria with angio-oedema affecting the head and neck, which could potentially compromise the airway, should be treated promptly with adrenaline (epinephrine). Stridor, odynophagia, dysphagia, or respiratory distress may be signs of laryngeal oedema, which can lead to respiratory arrest. The status of the airway should be assessed and closely monitored in all patients with angio-oedema, and all necessary steps must be taken to ensure the airway is always secured. In severe cases, consultation with an airway management specialist, for example an anaesthetist or otolaryngologist may be necessary. Airway compromise in patients with hereditary angio-oedema is beyond the scope of this topic and guidelines should be consulted for more detail.[26]​​

Angio-oedema in the absence of urticaria

Angio-oedema that occurs in the absence of urticaria, especially when involving airway compromise, mandates consideration for serious conditions, such as:

  • Hereditary angio-oedema (HAE; due to inhibition of the complement/kinin metabolism):

    • Typically lasts for a few days

    • Often described as painful.[27]​​

  • Acquired angio-oedema (with C1 inhibitor consumption from secondary causes, such as malignancy/autoimmune disease):

    • Patients may show signs and symptoms of malignancy/autoimmune disease pathologies.

  • Angio-oedema with normal C1 inhibitor:

    • May be drug-induced, e.g., due to angiotensin-converting-enzyme inhibitors. Often starts within weeks of starting the drug, but a significant number of patients are asymptomatic for years before the onset of swelling.

Recognition is paramount, as these patients are unlikely to respond to adrenaline (epinephrine) and require C1 inhibitor replacement or bradykinin-blocking agents.[3]​​[4][27]​​ Patients with HAE should, at a minimum, have access to emergency rescue medication (dependent on local availability) in the event of attacks. Generally, these patients should be managed by clinicians who are experienced with managing HAE. Airway compromise in patients with hereditary angio-oedema is beyond the scope of this topic and guidelines should be consulted for more detail.[26]​​

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