Synopsis
Recognise reproducible physical urticaria phenotypes, use controlled provocation safely, reduce trigger risk without disabling avoidance, and treat symptoms with non-sedating antihistamines.
- A consistent stimulus-to-wheal relationship distinguishes inducible urticaria; document delay, threshold, duration and whether symptoms extend beyond exposed skin.
- Symptomatic dermographism causes itchy linear wheals after stroking, whereas simple dermographism without symptoms does not require treatment.
- Cholinergic urticaria produces small itchy wheals with heat, emotion or exercise; systemic exertional symptoms require evaluation for exercise-induced anaphylaxis.
- Cold urticaria carries a particular risk during swimming or whole-body cooling, so unsupervised immersion challenge is unsafe.
- Provocation tests should reproduce the suspected trigger in a controlled graded way with emergency readiness when systemic reactions are plausible.
- Management combines realistic trigger modification, a regular second-generation H1 antihistamine and a written emergency plan for higher-risk phenotypes.
- Inducible urticarias must be assessed by lesion duration, onset, distribution, symptoms, mucosal findings, systemic physiology and the full medicine timeline rather than by colour alone.
- For Inducible urticarias, document the working diagnosis, excluded emergencies, uncertain culprit or trigger, treatment response and the exact safety-net given.
Key red flags
Syncope in water, throat symptoms after cold food, exertional collapse, systemic symptoms with heat, or swelling beyond the provoked site requires urgent allergy assessment and an emergency plan.
Generalised wheals, dizziness, breathing difficulty or collapse with swimming indicates anaphylaxis risk and requires strict safety planning.
Investigation priorities
Establish reproducibility, latency, threshold and cofactors before challenge.
Management branches
Wheals remain local, physiology is normal and a consistent physical trigger is identifiable.
- Document the stimulus, latency and threshold, then perform a low-risk standardised provocation when confirmation will change behaviour or treatment.
- Modify exposure proportionately using protective layers, load breaks, temperature planning or contact substitution instead of prohibiting all activity.
- Use a regular non-sedating H1 antihistamine when symptoms persist, measure control and reconsider coexisting spontaneous urticaria.
Key medicines
Cetirizine 10 mg tabletsAdults and adolescents aged 12 years and over take 10 mg orally once daily, with renal dose adjustment according to the SmPC.Check somnolence, driving, alcohol, renal function, pregnancy and breastfeeding; specialist-supervised doses above the licence remain off-label and require documented discussion.
Adrenaline auto-injector 300 microgramsAdults at risk use one 300 microgram intramuscular auto-injector into the outer thigh at anaphylaxis onset and call emergency services; use a second after five minutes if not improving.Device strength must match the individual; train with the exact brand, carry two devices, check expiry, inject through clothing if necessary and never rely on antihistamine first.