Dermatology · PANCE / PANRE

Urticaria (Acute and Chronic)

Transient pruritic edematous wheals from mast cell degranulation; acute (<6 wks) or chronic (≥6 wks).

Also known as: urticaria, hives, wheals, chronic spontaneous urticaria, CSU, angioedema

Overview

An inflammatory disorder of the dermis characterized by transient, pruritic, edematous wheals (hives), each lasting <24 hours, with normal-appearing skin between flares. Often accompanied by angioedema (deeper dermal/subcutaneous edema). Classified by duration: acute (<6 weeks) and chronic (≥6 weeks).

Epidemiology

Lifetime prevalence ~20% for acute urticaria. Chronic spontaneous urticaria (CSU) affects ~0.5-1% of adults; female predominance 2:1; peak ages 20-40.

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Risk factors

Acute: viral infections (most common in children), foods (peanuts, tree nuts, shellfish, eggs, dairy, soy), medications (NSAIDs, antibiotics, opioids, contrast media), insect stings, latex
Chronic spontaneous: autoimmune disease (thyroid disease in 25%, ANA positive in ~30%, autoimmune antibodies against FcεRI or IgE), atopic disease, stress
Chronic inducible: physical triggers (cold, heat, pressure, vibration, sun, water, exercise, cholinergic)
Drugs: NSAIDs, ACE inhibitors (angioedema without urticaria — bradykinin-mediated), opioids (direct mast cell activation)

Pathophysiology

Mast cell and basophil degranulation releases histamine, leukotrienes, prostaglandins, cytokines → vasodilation, increased capillary permeability, plasma extravasation into dermis (wheal) or deeper tissue (angioedema). Triggers: IgE-mediated (food/drug allergy), non-IgE immunologic (autoantibodies in CSU), direct mast cell activators (opioids, contrast), complement-mediated (urticarial vasculitis, hereditary angioedema), pseudoallergic (NSAIDs via COX-1 inhibition).

Clinical presentation

Symptoms

Intense pruritus (rarely burning or stinging)
Sudden onset of wheals lasting minutes to <24 hours each, fluctuating in location
Angioedema: face (lips, eyelids), hands, feet, genitalia, larynx — may compromise airway
Systemic symptoms (anaphylaxis): dyspnea, wheezing, syncope, GI distress — IM EPINEPHRINE

Signs / physical exam

Wheals: well-circumscribed raised pink or pale-centered plaques with surrounding flare; size mm to >10 cm; round, oval, polycyclic, annular; resolve without scarring or pigment change
Dermographism: linear wheal where skin is stroked — most common physical urticaria
Cholinergic urticaria: small (1-3 mm) wheals with surrounding flare after exercise, hot showers, emotional stress
Cold urticaria: wheal/angioedema in areas of cold contact; positive ice cube test
Angioedema: deeper, often asymmetric, non-pitting swelling of face, lips, tongue, extremities; LESS pruritic, more burning/painful

Classic findings

Transient migratory pruritic wheals lasting <24 hours each, with completely normal skin between.

Differential diagnosis

Urticarial vasculitis — Individual lesions >24 hours, painful/burning rather than itchy, residual purpura/pigmentation; biopsy = leukocytoclastic vasculitis; check complement, ANA, SSA, hep C
Erythema multiforme — Target lesions, dusky center, fixed >24 hours, mucosal involvement; HSV or drug trigger
Mastocytosis / mastocytoma — Persistent reddish-brown macules/papules with Darier sign (urticate on stroking); elevated tryptase
Hereditary angioedema (HAE) — Angioedema WITHOUT urticaria, family history, recurrent abdominal pain attacks, low C4 and C1-INH levels
ACE-inhibitor angioedema — Angioedema without urticaria, often facial/tongue, days to years after starting ACEi
Anaphylaxis — Urticaria + 1 more system: respiratory, hypotension, GI; rapid onset; epinephrine
Atopic dermatitis — Chronic eczematous lesions, lichenification, flexural; not transient
Contact urticaria — Wheals at site of contact with latex, food, plants; immediate or delayed

Diagnostic workup

Diagnostic criteria

Clinical: characteristic wheals lasting <24 hours each, total episode duration determines acute vs chronic; angioedema without urticaria requires HAE/ACEi workup.

Labs

Acute urticaria: usually no workup needed unless trigger unclear — careful history identifies most triggers (foods, drugs, infections)
Chronic spontaneous urticaria: limited testing per international guidelines — CBC with differential, CRP/ESR, TSH/free T4 and TPO antibodies (screen autoimmune thyroid)
If suspicion of urticarial vasculitis: skin biopsy, C3/C4, ANA, RF, hepatitis B/C, complement profile
If suspicion of hereditary angioedema: C4 (low during AND between attacks), C1-INH level and function, C1q
Autologous serum skin test or basophil activation test for autoimmune CSU (research/specialty)
Specific IgE / skin prick testing only for clinically suspected food/drug allergy with consistent history

Imaging

Not indicated

Diagnostic algorithm

flowchart TD
  A[Itchy wheal,<br/>each lasting <24 h] --> B{Duration of episode}
  B -->|<6 weeks| C[Acute urticaria]
  B -->|≥6 weeks| D[Chronic urticaria]
  C --> E[Identify trigger:<br/>infection, food, drug]
  D --> F[Limited workup: CBC, CRP, TSH, TPO Ab]
  E --> G[2nd-gen H1 antihistamine<br/>± short prednisone course]
  F --> G
  G --> H{Controlled in 2-4 wks?}
  H -->|No| I[Up-titrate H1 antihistamine<br/>to 4x dose]
  I --> J{Controlled?}
  J -->|No| K[Add omalizumab<br/>or cyclosporine]
  A --> L{Wheal lasts<br/>>24 h, painful,<br/>leaves purpura?}
  L -->|Yes| M[Urticarial vasculitis<br/>Biopsy + autoimmune workup]
  A --> N{Angioedema<br/>without wheals?}
  N -->|Yes| O[Check C4, C1-INH<br/>ACEi history → Hereditary AE or ACEi reaction]

Urticaria evaluation and step-care management algorithm.

Treatment

First-line

Identify and avoid trigger (when identified)
Step 1: second-generation non-sedating H1 antihistamine at standard dose — cetirizine 10 mg, levocetirizine 5 mg, fexofenadine 180 mg, loratadine 10 mg, desloratadine 5 mg, bilastine 20 mg daily
Step 2 (inadequate response after 2-4 weeks): up-titrate H1 antihistamine to 2-4x standard daily dose (EAACI/AAAAI guidelines)
Step 3: add omalizumab 300 mg SC every 4 weeks (anti-IgE biologic) — highly effective for CSU; alternatively trial cyclosporine 2-5 mg/kg/day
Step 4: cyclosporine or other immunomodulator (mycophenolate, dapsone)
Acute severe urticaria with angioedema: short course oral prednisone 0.5-1 mg/kg/day × 5-7 days (avoid long-term use)
Anaphylaxis or laryngeal angioedema: IM epinephrine 0.3-0.5 mg adult / 0.01 mg/kg pediatric in anterolateral thigh — first-line; airway, IV fluids, H1+H2 blockers, steroids as adjuncts

Chronic inducible (physical) urticaria

Identify trigger and avoid (cold, pressure, heat, sun, vibration)
Cold urticaria — cetirizine 4x daily, omalizumab, rupatadine; carry EpiPen
Cholinergic urticaria — antihistamines, avoid extreme exertion/heat
Solar urticaria — sun avoidance, broad-spectrum SPF 50+, antihistamines, phototherapy desensitization

Hereditary angioedema

Acute: IV C1 esterase inhibitor concentrate, ecallantide, icatibant
Prophylaxis: lanadelumab, berotralstat, attenuated androgens (danazol; rarely used now)
NOT responsive to antihistamines, epinephrine, or steroids

ACEi-induced angioedema

Discontinue ACE inhibitor permanently (cross-reactivity with ARBs ~10% — avoid if possible)
Supportive care; refractory cases may respond to icatibant

Second-line / adjunct

Avoid first-generation sedating antihistamines (diphenhydramine, hydroxyzine) as routine therapy — sedation, anticholinergic effects, and short half-life make them inferior to second-generation agents
H2 antagonist (famotidine) addition has modest benefit
Leukotriene receptor antagonist (montelukast) sometimes added, especially for NSAID-sensitive patients
Counsel: most chronic urticaria resolves within 1-5 years

Complications

Anaphylaxis with airway compromise — life-threatening
Sleep disturbance, decreased quality of life, depression, work/school impairment
Adverse effects from chronic systemic corticosteroids (avoid if possible)
Misdiagnosis as drug allergy → unnecessary medication restriction

PANCE pearls

Individual wheals lasting >24 hours, painful rather than itchy, with residual purpura = urticarial vasculitis — biopsy.
Angioedema WITHOUT urticaria → think hereditary angioedema or ACE inhibitor reaction; antihistamines and steroids do NOT work.
Up-titration of second-generation H1 antihistamines to 4x dose is safe, evidence-based, and recommended BEFORE adding other agents.
Omalizumab is the most effective add-on for chronic spontaneous urticaria refractory to high-dose antihistamines.
Acute urticaria + respiratory or hemodynamic symptoms = anaphylaxis = IM epinephrine FIRST, not antihistamines.

References

EAACI/GA²LEN/EDF/WAO 2022 — International EAACI/GA²LEN/EuroGuiDerm/APAAACI Guideline for the Definition, Classification, Diagnosis and Management of Urticaria (Zuberbier et al., Allergy 2022)
AAAAI/ACAAI 2014 — Practice Parameter Update: Chronic Urticaria (Bernstein et al., J Allergy Clin Immunol 2014)
WAO 2020 — World Allergy Organization Anaphylaxis Guidance 2020 (Cardona et al., World Allergy Organ J 2020)

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