What it is
Urticaria is an itchy raised rash of wheals that look like nettle stings, where each individual wheal fades within a day and new ones appear elsewhere. It is called acute when it has been present for under 6 weeks and chronic beyond that, and one group of patients has an inducible form brought on by scratching, pressure, heat, sweating, exercise, cold or water. Treatment rests on non-sedating antihistamines with the dose adjusted under supervision, a small and targeted set of tests rather than a broad allergy panel, and a clear written instruction about when a swelling needs emergency care instead of an appointment.
What this page covers
- Acute urticaria, with review of a possible drug, food or infection trigger — NSAIDs and antibiotics asked about directly
- Chronic spontaneous urticaria
- Inducible (physical) urticaria: dermographism, delayed pressure, cholinergic and heat-triggered, cold, exercise-induced and aquagenic forms
- Second-generation antihistamines and supervised up-dosing, with the effect on driving discussed
- A targeted workup, including thyroid autoimmunity, in place of broad allergy panels
- Referral for omalizumab or other second-line therapy where symptoms persist
- Recognition of urticarial vasculitis — a wheal fixed for more than a day, burning rather than itching, or leaving a bruise — and the biopsy threshold
- Angioedema: separating the histamine-mediated swelling that travels with urticaria from the bradykinin-mediated forms caused by ACE inhibitors or hereditary C1-inhibitor deficiency
- Practical advice for the heat- and sweat-triggered forms, which are genuinely limiting in this climate
- Written instructions on when to go to emergency care
Honestly
Most chronic urticaria has no findable external cause, and broad allergy panels usually mislead and push patients into food restriction that does not help. Any swelling of the lips, tongue or throat, difficulty breathing or faintness is emergency care and not a clinic appointment, and swelling without wheals in a patient taking an ACE inhibitor is a different mechanism that antihistamines do not touch.