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8/17/2025 • 12–18 min read

Urticaria & Angioedema: Triage, Triggers, and Treatment

Hives (wheals) come and go within 24 hours; angioedema is deeper, slower, and can threaten the airway. The first job is airway safety and distinguishing histamine-mediated frombradykinin-mediated angioedema (e.g., ACE-inhibitor, hereditary). Treatment diverges sharply.

ED Triage: Airway First

  • Red flags: voice change, stridor, drooling, dysphagia, tongue/floor-of-mouth swelling, hypotension, syncope.
  • Epinephrine IM (anterolateral thigh) for suspected anaphylaxis: adults 0.3–0.5 mg of 1 mg/mL (1:1000) q5–15 min as needed. Place on monitors, oxygen, two IV lines.
  • Lay flat if hypotensive, elevate legs, start IV fluids (balanced crystalloids) if shocky.

Histamine vs Bradykinin: How to Tell

  • Histamine-mediated: often urticaria present, pruritus, response to epinephrine/antihistamines/steroids; triggers include foods, drugs (NSAIDs, antibiotics), stings, infections.
  • Bradykinin-mediated (ACE-i, ARB rarely, hereditary/acquired C1-inhibitor deficiency):no hives, prominent facial/tongue/abdominal swelling, poor response to epinephrine/antihistamines/steroids, family history or ACE-i use.

Acute Treatment (non-anaphylaxis histaminergic)

  • Second-generation H1 antihistamine (non-sedating) first line:cetirizine 10 mg daily (can up-titrate), fexofenadine 180 mg daily, loratadine 10 mg daily. Prefer cetirizine/fexofenadine for faster onset.
  • Up-titration (short term, clinician-guided): increase H1 dose up to 4× label if needed (e.g., cetirizine 20 mg BID or fexofenadine 360 mg BID) while monitoring sedation/QT risks (low with these agents).
  • Adjuncts: H2 blocker (e.g., famotidine), leukotriene antagonist (montelukast) for NSAID-exacerbated disease.
  • Short steroid burst (e.g., prednisone 30–50 mg/day for 3–5 days) for severe flares; avoid prolonged or repeated courses.

Anaphylaxis Bundle (when systemic symptoms)

  • Epinephrine IM first; then airway/oxygen/IV fluids.
  • Add H1 (cetirizine/levocetirizine) ± H2 (famotidine) and a single dose of steroid to reduce biphasic risk (evidence mixed; still common practice).
  • Observe 4–6 h (longer if severe/asthma/β-blockers). Discharge with two epinephrine auto-injectors, written plan, and trigger counseling.

Bradykinin Angioedema (ACE-i or C1-INH mediated)

  • Airway early—low threshold for advanced airway if tongue/laryngeal edema.
  • Stop ACE inhibitor permanently if suspected.
  • Targeted therapy (where available): icatibant (B2 antagonist), C1-esterase inhibitor concentrate, or ecallantide. Fresh frozen plasma is a backup in some protocols if specific agents unavailable.
  • Antihistamines/steroids/epinephrine have limited effect in pure bradykinin disease but give epinephrine if any doubt of anaphylaxis or airway compromise.
  • Clues to HAE/acquired C1-INH deficiency: recurrent angioedema without hives, abdominal attacks, family history. Outpatient testing: low C4, low/abnormal C1-INH (level/function).

Chronic Spontaneous Urticaria (CSU): Simple Algorithm

  1. Step 1: daily second-generation H1 (cetirizine/fexofenadine/loratadine).
  2. Step 2: up-titrate H1 up to 4× standard dose.
  3. Step 3: add omalizumab (anti-IgE) for refractory CSU (monthly dosing; monitor for rare anaphylaxis).
  4. Step 4: consider cyclosporine under specialist care if still refractory.

Routine extensive labs are low yield; targeted tests (CBC, ESR/CRP, TSH) when history suggests.

Common Triggers & Phenotypes

  • Infections (viral/URI), foods, medications (NSAIDs, antibiotics, contrast), stings.
  • Physical urticarias: cold, pressure, cholinergic (heat/exercise), solar, aquagenic—treat with avoidance + antihistamines; consider omalizumab in refractory cases.
  • Autoimmune thyroid disease association with CSU—check TSH if clues.

Pediatrics Notes

  • Weight-based dosing; prefer second-generation H1s. Avoid codeine/opiates. Evaluate for anaphylaxis carefully.
  • Teach caregivers epinephrine auto-injector technique if indicated.

Discharge & Education

  • Written plan: when to use epinephrine, max antihistamine doses, and when to seek urgent care.
  • Trigger diary, label reading (NSAIDs/foods), avoid alcohol/heat in flares.
  • Return immediately for tongue/throat swelling, breathing difficulty, dizziness/syncope.

Patient FAQs

“Are steroids the cure?” No—use only briefly for severe flares. The backbone is non-sedating antihistamines (up-titrated) and biologics for chronic cases.

“Do I need allergy testing?” Often not for chronic spontaneous urticaria; targeted testing only when history points to a specific allergen.

References & Notes

Practical pathway: airway-first logic, epinephrine for anaphylaxis, high-dose second-gen H1 antihistamines, limited steroids, and bradykinin-specific therapy when indicated. Minimal, history-guided workup. Local protocols vary—follow institutional guidance. Educational only.

Educational only, not personal medical advice.