Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Diagnose wheal-based acute and chronic spontaneous urticaria, identify anaphylaxis and alternative inflammatory disease, investigate selectively, and use a safe stepwise antihistamine strategy.
Confirm that lesions are true wheals by asking the patient to mark or photograph one and checking whether it disappears within a day. Angioedema may accompany wheals and last longer. A six-week duration separates acute from chronic disease for classification, but emergency assessment always depends on current airway, breathing and circulation.
History should cover infections, NSAIDs and other medicines, temporal food or sting exposure, physical triggers, angioedema without wheals, fever, weight loss and autoimmune symptoms. In otherwise typical chronic spontaneous urticaria, extensive allergy, infection or imaging panels have low yield. Focused FBC and inflammatory markers may be considered when the history is atypical or disease is persistent.
Clinical decisions in Acute and chronic spontaneous urticaria depend on trajectory and consequence. Re-examine evolving skin, repeat focused systemic assessment when the patient changes, and reconcile every result with morphology and timing; a normal early test cannot neutralise worsening pain, mucosal injury or organ dysfunction.
Most acute episodes follow infection, medicines or an unconfirmed trigger, while chronic spontaneous urticaria reflects recurrent mast-cell activation without a reproducible external stimulus.
Some chronic disease involves IgG autoantibodies to IgE pathways or IgE directed at self-antigens, but routine clinical autoantibody testing does not reliably direct initial care.
NSAIDs can aggravate active urticaria and alcohol, heat, infection or stress may lower the threshold without representing a true IgE allergy.
Mast-cell mediators dilate superficial dermal vessels and increase permeability, producing an itchy raised wheal with surrounding erythema or colour change.
Mediator release resolves locally while recurring elsewhere, so each ordinary wheal fades within twenty-four hours without leaving bruising or scale.
The same pathway in deeper dermis and subcutis produces angioedema that is more painful or tight, less itchy and can last up to several days.
Repeated signalling sensitises skin and sleep, work and mood deteriorate even though wheals themselves remain transient and non-scarring.
Raised itchy lesions vary in size and shape, blanch variably across skin tones, migrate and leave normal skin within twenty-four hours.
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.
Painful or burning fixed lesions lasting longer than a day, residual bruising, fever or joint and renal symptoms are not typical simple urticaria.
Sleep loss, work absence and distress can be severe despite a normal examination between attacks; patient photographs and activity scores can capture disease.
Lesions lasting beyond twenty-four hours, burning or pain, bruising and systemic symptoms suggest small-vessel inflammation and justify directed tests or biopsy.
Wheals reproducibly linked to stroking, cold, heat, exercise, pressure, water or light require a provocation history and sometimes supervised challenge.
Recurrent flushing, syncope, fever, bone pain or persistently raised tryptase broadens assessment beyond uncomplicated spontaneous urticaria.
Morbilliform drug eruption, eczema and viral exanthem persist in fixed sites and usually lack the evanescent raised morphology of a wheal.
Acute mast-cell activation may progress to life-threatening airway, respiratory or circulatory compromise and requires adrenaline rather than antihistamine-only treatment.
Night-time itch, unpredictable swelling and visible lesions impair sleep, attendance, concentration, relationships and psychological wellbeing in chronic disease.
Attributing chronic spontaneous urticaria to multiple foods can lead to unsafe dietary restriction, anxiety and misleading allergy records without improving control.
Sedating antihistamines impair driving and cognition, while repeated systemic corticosteroids expose patients to metabolic, psychiatric, bone and infection harms.
Transient wheals may have vanished by examination, so accurately timed patient photographs and a lesion diary can preserve decisive evidence.
Histaminergic swelling can remain for up to seventy-two hours even though associated superficial wheals resolve within one day.
Cyclo-oxygenase-1 inhibition can worsen active chronic urticaria without implying a classic drug-specific IgE mechanism.
In deeply pigmented skin a wheal may be easier to feel and see through swelling than through surrounding redness.
Once stable remission is sustained, reduce treatment cautiously to test ongoing need rather than assuming indefinite maximal dosing.
Diagnosing food allergy from one coincidental meal during a period of daily spontaneous wheals.
Using chlorphenamine or another sedating antihistamine chronically without discussing cognition, falls and driving.
Treating airway compromise with antihistamine while delaying intramuscular adrenaline.
Calling painful bruising lesions ordinary urticaria without considering vasculitis and systemic assessment.
Escalating doses without checking whether the patient takes the medicine regularly or whether lesions truly behave like wheals.
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A 35-year-old has itchy raised lesions on most days for nine weeks. Each spot disappears within six hours and new lesions arise elsewhere. There is no reproducible trigger or systemic illness. What is the most likely classification?
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes
Somnolence can occur; consider driving, alcohol, renal impairment, pregnancy, breastfeeding and additive sedation, and do not exceed the licensed dose without supervised off-label planning.
Use caution in older people and renal or hepatic impairment; fruit juice and aluminium or magnesium antacids affect absorption timing, and cardiac history deserves review.