Hives (Urticaria): Triggers, Duration, and When to Seek Care

Hives are transient, pruritic wheals caused by mast cell degranulation and histamine release. They typically last <24 hours per lesion but can recur for days to weeks (acute) or >6 weeks (chronic).

Common Triggers

• Allergic – Foods (nuts, shellfish, eggs), medications (penicillin, NSAIDs), insect venom, latex.
• Physical – Pressure, cold, heat, sunlight, vibration, exercise (cholinergic).
• Infections – Viral (URI, hepatitis), bacterial (strep), parasitic.
• Autoimmune – Chronic spontaneous urticaria (CSU) often has autoantibodies to FcεRI or IgE.
• Stress – Neuroendocrine modulation of mast cells.

Management

• Second-gen H1 antihistamines (cetirizine, loratadine, fexofenadine) – up to 4× dose for CSU.
• H2 blockers (famotidine), leukotriene antagonists (montelukast) as add-on.
• Short-course oral steroids for severe flares.
• Omalizumab (anti-IgE) for refractory CSU.

Red Flags → ER

• Angioedema of tongue/lips/airway
• Dyspnea, wheeze, stridor
• Syncope, hypotension (anaphylaxis)

Keep a trigger diary; see an allergist/immunologist for chronic or recurrent cases.