PassFinals
Dermatology

Urticaria

Mast-cell mediator release causes short-lived, itchy, blanching weals; histaminergic angioedema and anaphylaxis can accompany urticaria, while isolated angioedema may instead be bradykinin-mediated and needs a different pathway.

In a nutshell

Mast-cell mediator release causes itchy, transient, blanching weals. Histaminergic angioedema may accompany urticaria, but isolated prolonged angioedema can be bradykinin-mediated; anaphylaxis is a systemic airway, breathing or circulation emergency.

Classic presentation

Sudden-onset itchy, raised, blanching weals, each fading within 24 hours, sometimes with associated swelling of the lips or eyes.

Key points

  • Urticaria and histaminergic angioedema may share a mast-cell mechanism; isolated angioedema without weals can be bradykinin-mediated and needs a different pathway.
  • An individual weal resolving within 24 hours is the hallmark; weals lasting longer or bruising suggest urticarial vasculitis instead.
  • Chronic spontaneous urticaria is defined by symptoms recurring for six weeks or more and is usually not explained by a single food allergy.
  • If a standard-dose non-sedating antihistamine fails, the dose can be increased up to fourfold before it is considered to have failed.
  • Omalizumab is a specialist escalation for severe chronic spontaneous urticaria that remains uncontrolled despite appropriate antihistamine treatment; ciclosporin is a further specialist option.
  • A short course of oral corticosteroid can settle a severe acute flare but is not used for long-term control.
  • Anaphylaxis needs adrenaline, not antihistamines, because only adrenaline reverses airway and circulatory compromise quickly enough.

First-line investigation

None routinely: diagnose clinically from the transient weal pattern and duration. Investigate only when there is a specific suspected allergy, atypical disease, systemic features or possible bradykinin-mediated angioedema.

Management

Exclude anaphylaxis and dangerous angioedema

  • Assess airway, breathing and circulation whenever urticaria is accompanied by rapid swelling, wheeze, respiratory distress, hypotension or collapse; give intramuscular adrenaline immediately for suspected anaphylaxis and seek emergency help.3,4

Diagnose clinically and avoid indiscriminate testing

  • Confirm that individual weals resolve within 24 hours and ask about reproducible triggers, medicines, angioedema and systemic features; do not order broad allergy panels without a focused history.1,2

Use regular non-sedating antihistamine treatment

  • Use a regular non-sedating H1 antihistamine for ongoing symptoms; if control is inadequate, specialist guidance may support increasing the same agent up to four times the standard dose where appropriate.1,2,6

Refer refractory chronic spontaneous urticaria

  • Refer severe chronic spontaneous urticaria that remains uncontrolled despite appropriate antihistamine treatment for specialist assessment of omalizumab; ciclosporin is a further specialist option with monitoring and shared risk assessment.5,2,6

Review atypical disease and quality of life

  • Review symptom burden, sleep and quality of life, and reassess the diagnosis or refer when lesions are fixed, painful, bruise, leave pigment, have systemic features, or when isolated angioedema is prolonged or antihistamine-unresponsive.1,2,4

Exam traps

  • A weal lasting more than 24 hours or leaving bruising is not typical urticaria: think urticarial vasculitis.
  • Angioedema without weals is still mast-cell mediated disease and can threaten the airway even without a rash.
  • Sedating antihistamines are not first line for routine urticaria management; non-sedating agents are preferred.
  • A short course of oral corticosteroid may help a severe flare but is not appropriate for long-term maintenance.

Illustrations

Urticarial wealsClinical photograph of raised, erythematous, blanching weals with pale centres typical of acute urticaria.James Heilman, MD, Wikimedia Commons · CC-BY-SA-3.0
Mast cell degranulation mechanismDiagram showing mast cell triggers converging on histamine release, causing vasodilation, vascular leak and nerve stimulation in the dermis.PassFinals · original
AngioedemaClinical photograph of diffuse, non-pitting swelling of the lips or periorbital area representing deeper mast-cell mediator release.James Heilman, MD, Wikimedia Commons · CC-BY-SA-3.0

Key sources

  1. NICE CKS: Urticaria (Current UK primary-care topic for clinical diagnosis, trigger assessment, antihistamine treatment, escalation and referral; professional access may require NHS or institutional login.)
  2. British Association of Dermatologists: Guidelines for chronic urticaria (2021) (UK specialist dermatology guideline covering chronic urticaria assessment, patient-centred outcome measurement, high-dose non-sedating antihistamines, omalizumab, ciclosporin and specialist care; published online in 2022 as the 2021 guideline.)
  3. Resuscitation Council UK: Emergency treatment of anaphylactic reactions (2021) (Current RCUK healthcare-provider guideline for immediate recognition and treatment of anaphylaxis, including intramuscular adrenaline and escalation; the RCUK page identifies the 2021 version as the most recent anaphylaxis guideline.)
  4. NICE CKS: Angioedema (UK primary-care topic used to distinguish histaminergic and bradykinin-mediated angioedema and identify ACE-inhibitor or hereditary-angioedema pathways; professional access may require NHS or institutional login.)
  5. NICE TA339: Omalizumab for previously treated chronic spontaneous urticaria (NICE technology appraisal supporting specialist add-on omalizumab for severe chronic spontaneous urticaria in eligible adults and young people aged 12 years or over, with objective severity assessment and stopping rules.)
  6. BNF online: current antihistamine, corticosteroid, omalizumab and ciclosporin prescribing (Use the current BNF and local specialist protocol for age-appropriate drug selection, dosing, interactions, contraindications, monitoring and treatment duration; no fixed regimen is reproduced here.)

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.