Acute and chronic spontaneous urticaria

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

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.

Key points

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.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Spontaneous mast-cell activation

Most acute episodes follow infection, medicines or an unconfirmed trigger, while chronic spontaneous urticaria reflects recurrent mast-cell activation without a reproducible external stimulus.

Autoimmune endotypes

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.

Medicine and cofactor effects

NSAIDs can aggravate active urticaria and alcohol, heat, infection or stress may lower the threshold without representing a true IgE allergy.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Histamine-mediated oedema
Mast-cell mediators dilate superficial dermal vessels and increase permeability, producing an itchy raised wheal with surrounding erythema or colour change.
2
Transient lesion migration
Mediator release resolves locally while recurring elsewhere, so each ordinary wheal fades within twenty-four hours without leaving bruising or scale.
3
Deeper tissue involvement
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.
4
Chronic amplification
Repeated signalling sensitises skin and sleep, work and mood deteriorate even though wheals themselves remain transient and non-scarring.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Evanescent itchy wheals

Raised itchy lesions vary in size and shape, blanch variably across skin tones, migrate and leave normal skin within twenty-four hours.

Associated histaminergic swellingRed flag

Eyelid or lip angioedema accompanying wheals supports mast-cell disease, but tongue or laryngeal symptoms demand immediate ABC assessment.

Anaphylaxis physiologyRed flag

Sudden wheals plus throat tightness, wheeze, hypoxia, hypotension or collapse constitute suspected anaphylaxis and need intramuscular adrenaline.

Vasculitic departure

Painful or burning fixed lesions lasting longer than a day, residual bruising, fever or joint and renal symptoms are not typical simple urticaria.

Chronic burden

Sleep loss, work absence and distress can be severe despite a normal examination between attacks; patient photographs and activity scores can capture disease.

Red flags requiring action

Airway swelling, wheeze, hypoxia, hypotension, syncope, severe abdominal symptoms after an allergen, fever, bruising, painful fixed lesions or systemic illness require urgent reassessment.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Timed lesion history and patient photographsFirst step
Why
Confirm that individual lesions are transient wheals rather than a fixed exanthem.
Interpretation and limitations
Record onset and disappearance of the same lesion; images require consent and may under-represent elevation or erythema in darker skin.
02
Focused trigger and medicine history
Why
Separate spontaneous disease, immediate allergy, NSAID aggravation and inducible forms.
Interpretation and limitations
Temporal association must be reproducible and biologically plausible; coincidental food exposure is common during frequent chronic attacks.
03
FBC, CRP or ESR when clinically indicated
Why
Look for inflammation, cytopenia or an alternative systemic process in persistent or atypical disease.
Interpretation and limitations
Normal results support but do not prove uncomplicated disease; eosinophilia alone neither identifies a food nor confirms parasitic infection.
04
Skin biopsy of a suitable persistent lesion
Why
Assess suspected urticarial vasculitis or another fixed inflammatory eruption.
Interpretation and limitations
Biopsy is not routine for transient wheals; select a fresh fixed lesion and consider direct immunofluorescence with laboratory advice.
05
Baseline tests before specialist immunomodulation
Why
Meet medicine-specific safety requirements and quantify severity.
Interpretation and limitations
The required tests depend on proposed treatment and comorbidity; do not delay symptomatic antihistamine treatment while arranging routine specialist work-up.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Urticarial vasculitis

Lesions lasting beyond twenty-four hours, burning or pain, bruising and systemic symptoms suggest small-vessel inflammation and justify directed tests or biopsy.

Inducible urticaria

Wheals reproducibly linked to stroking, cold, heat, exercise, pressure, water or light require a provocation history and sometimes supervised challenge.

Mast-cell and autoinflammatory disease

Recurrent flushing, syncope, fever, bone pain or persistently raised tryptase broadens assessment beyond uncomplicated spontaneous urticaria.

Non-urticarial exanthem

Morbilliform drug eruption, eczema and viral exanthem persist in fixed sites and usually lack the evanescent raised morphology of a wheal.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01ABC emergencyTreat suspected anaphylaxisFirst stepWheals or angioedema occur with airway, breathing or circulation compromise or rapidly progressive systemic symptoms.

1Call for help, lie the patient flat with legs raised unless breathing requires a supported sitting position, and do not allow standing or walking.
2Give intramuscular adrenaline in the anterolateral thigh and repeat after five minutes when life-threatening features persist while providing oxygen and monitoring.
3After stabilisation, observe according to risk, document likely trigger, arrange specialist referral and supply auto-injectors with training when indicated.

02Typical spontaneous diseaseSuppress wheals safelyTransient itchy wheals occur without anaphylaxis, vasculitic features or a reproducible physical trigger.

1Explain lesion timing, review aggravating medicines and use a regular licensed non-sedating second-generation H1 antihistamine rather than intermittent sedating treatment.
2EscalationIf control remains inadequate, confirm adherence and diagnosis before supervised off-label escalation up to fourfold or specialist referral.
3Measure control and quality-of-life impact, then step treatment down after sustained remission instead of continuing maximal therapy automatically.

03Atypical or refractory courseReopen diagnosis and escalateEscalationLesions persist, bruise, hurt, accompany fever or organ symptoms, or remain uncontrolled despite a verified antihistamine strategy.

1Repeat full skin and systemic assessment, select focused blood tests and biopsy when urticarial vasculitis or another inflammatory disorder is plausible.
2Refer chronic refractory disease for specialist consideration of omalizumab or other immunomodulation using treatment-specific eligibility and monitoring.
3Avoid serial empirical corticosteroid courses that suppress signs temporarily while accumulating harm and delaying a secure phenotype.

Key medicines and prescribing safety2 treatments · regimens, roles and cautions

A licensed non-sedating second-generation H1 antihistamine for urticaria symptom suppression and a practical regular starting regimen.

Cetirizine 10 mg tablets

Adults and adolescents aged 12 years and over take 10 mg orally once daily; reduce according to renal function and the product information.

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.

Another licensed, generally non-sedating H1 antihistamine when an individual response or tolerability makes it suitable.

Fexofenadine 180 mg tablets

Adults and children aged 12 years and over take 180 mg orally once daily before a meal for chronic idiopathic urticaria.

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.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Anaphylaxis

Acute mast-cell activation may progress to life-threatening airway, respiratory or circulatory compromise and requires adrenaline rather than antihistamine-only treatment.

Sleep and functional loss

Night-time itch, unpredictable swelling and visible lesions impair sleep, attendance, concentration, relationships and psychological wellbeing in chronic disease.

Unnecessary allergy restriction

Attributing chronic spontaneous urticaria to multiple foods can lead to unsafe dietary restriction, anxiety and misleading allergy records without improving control.

Treatment adverse effects

Sedating antihistamines impair driving and cognition, while repeated systemic corticosteroids expose patients to metabolic, psychiatric, bone and infection harms.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Use the Urticaria Control Test or a comparable symptom record to track wheal days, itch, angioedema, sleep and daily function.
Review adherence, sedation, renal function where relevant, NSAID exposure and whether each lesion still resolves within twenty-four hours.
After off-label antihistamine up-dosing or specialist therapy, document benefit and adverse effects before continuing or escalating.
At every review of Acute and chronic spontaneous urticaria, record lesion evolution, new mucosal or systemic features, medicine changes, treatment adherence and adverse effects.
Give a named route for urgent reassessment if breathing, circulation, fever, skin pain, blistering, facial swelling, reduced urine output or other organ symptoms develop during Acute and chronic spontaneous urticaria.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

A quiet clinic visit proves little

Transient wheals may have vanished by examination, so accurately timed patient photographs and a lesion diary can preserve decisive evidence.

Angioedema lasts longer

Histaminergic swelling can remain for up to seventy-two hours even though associated superficial wheals resolve within one day.

NSAIDs often aggravate

Cyclo-oxygenase-1 inhibition can worsen active chronic urticaria without implying a classic drug-specific IgE mechanism.

Colour is not the definition

In deeply pigmented skin a wheal may be easier to feel and see through swelling than through surrounding redness.

Control enables stepping down

Once stable remission is sustained, reduce treatment cautiously to test ongoing need rather than assuming indefinite maximal dosing.

11Common pitfallsFrequent interpretation and management errors.

01
Diagnosing food allergy from one coincidental meal during a period of daily spontaneous wheals.
02
Using chlorphenamine or another sedating antihistamine chronically without discussing cognition, falls and driving.
03
Treating airway compromise with antihistamine while delaying intramuscular adrenaline.
04
Calling painful bruising lesions ordinary urticaria without considering vasculitis and systemic assessment.
05
Escalating doses without checking whether the patient takes the medicine regularly or whether lesions truly behave like wheals.