Synopsis
Diagnose wheal-based acute and chronic spontaneous urticaria, identify anaphylaxis and alternative inflammatory disease, investigate selectively, and use a safe stepwise antihistamine strategy.
- A wheal is raised, itchy and transient; an individual ordinary urticarial lesion resolves within twenty-four hours, although new wheals can appear elsewhere.
- Acute urticaria lasts up to six weeks; recurrent wheals on most days beyond six weeks define chronic urticaria and require phenotype-led review.
- Chronic spontaneous urticaria is usually not caused by an external allergen, so routine broad food panels and restrictive diets are unhelpful.
- Use a regular non-sedating second-generation H1 antihistamine at its licensed dose; specialist-guided escalation may include off-label dose increase up to fourfold.
- Omalizumab is a specialist option for eligible severe chronic spontaneous urticaria after inadequate response to standard treatment; continuation requires documented response.
- Avoid routine long-term oral corticosteroids because benefit is temporary and cumulative toxicity is substantial.
- Acute and chronic spontaneous urticaria must be assessed by lesion duration, onset, distribution, symptoms, mucosal findings, systemic physiology and the full medicine timeline rather than by colour alone.
- For Acute and chronic spontaneous urticaria, document the working diagnosis, excluded emergencies, uncertain culprit or trigger, treatment response and the exact safety-net given.
Key red flags
Airway swelling, wheeze, hypoxia, hypotension, syncope, severe abdominal symptoms after an allergen, fever, bruising, painful fixed lesions or systemic illness require urgent reassessment.
Eyelid or lip angioedema accompanying wheals supports mast-cell disease, but tongue or laryngeal symptoms demand immediate ABC assessment.
Sudden wheals plus throat tightness, wheeze, hypoxia, hypotension or collapse constitute suspected anaphylaxis and need intramuscular adrenaline.
Investigation priorities
Confirm that individual lesions are transient wheals rather than a fixed exanthem.
Management branches
Wheals or angioedema occur with airway, breathing or circulation compromise or rapidly progressive systemic symptoms.
- Call for help, lie the patient flat with legs raised unless breathing requires a supported sitting position, and do not allow standing or walking.
- Give intramuscular adrenaline in the anterolateral thigh and repeat after five minutes when life-threatening features persist while providing oxygen and monitoring.
- After stabilisation, observe according to risk, document likely trigger, arrange specialist referral and supply auto-injectors with training when indicated.