Residency · Residency · Dermatology

Urticaria and Angioedema: Acute and Chronic

Overview

Urticaria (hives) is characterized by transient, pruritic, edematous wheals arising from superficial dermal edema, while angioedema involves deeper dermal and subcutaneous swelling. Acute urticaria (lasting less than 6 weeks) is common and usually self-limited, whereas chronic urticaria (persisting beyond 6 weeks) affects approximately 1 percent of the population and can be profoundly debilitating. Understanding mast cell biology and the distinction between histaminergic and non-histaminergic pathways is essential for management.

Classification

By Duration

Acute urticaria lasts less than 6 weeks and has an identifiable trigger in about 50 percent of cases, including infections, drugs, and foods. Chronic urticaria persists beyond 6 weeks with wheals occurring most days and is subdivided into chronic spontaneous urticaria (CSU), where no identifiable external trigger exists, and chronic inducible urticaria (CIndU), where a reproducible physical stimulus causes the reaction.

Chronic Inducible Urticaria Subtypes

Symptomatic dermatographism is the most common physical urticaria, producing wheals from stroking or friction. Cold urticaria produces wheals on rewarming after cold exposure and is diagnosed with the ice cube test. Delayed pressure urticaria causes deep swelling 4 to 6 hours after sustained pressure. Solar urticaria produces wheals within minutes of sun exposure. Cholinergic urticaria produces small (2 to 4 mm) punctate wheals triggered by sweating, exercise, or hot water. Aquagenic urticaria produces tiny wheals from water contact regardless of temperature. Vibratory urticaria and angioedema are triggered by vibratory stimuli.

Pathophysiology

Mast Cell Degranulation

The central event in urticaria is mast cell release of both preformed and newly synthesized mediators. Preformed mediators released immediately include histamine, tryptase, heparin, and TNF-alpha. Newly synthesized mediators include prostaglandin D2, leukotriene C4, and PAF. Late-phase mediators include the Th2 cytokines IL-4, IL-5, and IL-13. Histamine acts on H1 receptors on endothelial cells, causing vasodilation and increased permeability (producing the wheal), and on sensory nerves, causing pruritus.

Mechanisms of Mast Cell Activation

Several pathways can activate mast cells. In classic IgE-mediated (type I) hypersensitivity, allergen cross-links IgE on the mast cell's FcepsilonRI receptor. In autoimmune type I (type IIb) CSU, IgE autoantibodies target self-antigens such as thyroid peroxidase, IL-24, or dsDNA. In autoimmune type IIb, IgG autoantibodies target FcepsilonRI or IgE itself — found in approximately 30 to 40 percent of CSU patients and detectable by the autologous serum skin test (ASST) or basophil activation test. Complement-mediated activation involves C5a acting as an anaphylatoxin, as seen in serum sickness and urticarial vasculitis. Direct mast cell degranulation through the MRGPRX2 receptor pathway is caused by opioids, radiocontrast, and vancomycin. NSAID-induced urticaria occurs when COX-1 inhibition shunts arachidonic acid toward the leukotriene pathway.

Angioedema Pathophysiology

Histaminergic angioedema accompanies urticaria and is mast cell-mediated. Bradykinin-mediated angioedema, however, is not associated with urticaria or pruritus and has distinct causes: ACE inhibitor-induced angioedema occurs because ACE normally degrades bradykinin, and its inhibition leads to bradykinin accumulation; hereditary angioedema (HAE) results from C1-inhibitor deficiency or dysfunction (types I and II) or factor XII gain-of-function mutations; and acquired C1-INH deficiency is associated with lymphoproliferative disorders.

Clinical Features

Urticaria

Wheals are circumscribed, erythematous, edematous papules and plaques. Individual wheals characteristically last less than 24 hours and resolve without residual marks. If a wheal lasts longer than 24 hours or leaves bruising or purpura, urticarial vasculitis should be considered. Wheals are intensely pruritic (not painful, unless vasculitic) and can occur anywhere on the body. Dermographism is often elicitable.

Angioedema

Angioedema presents as non-pitting, asymmetric swelling of the deep dermis and subcutis, with predilection for the lips, eyelids, tongue, genitalia, and extremities. Histaminergic angioedema is pruritic and often accompanies urticaria. Bradykinin-mediated angioedema is non-pruritic and painful or burning, with no associated urticaria. Laryngeal edema is a medical emergency regardless of mechanism.

Diagnostic Workup

Acute Urticaria

This is usually a clinical diagnosis requiring no routine labs. The trigger is identified through detailed history (foods, drugs, infections, insect stings), and IgE-mediated allergy testing is pursued if consistent triggers are identified.

Chronic Spontaneous Urticaria

Routine labs should be limited and guided by clinical suspicion: CBC with differential, ESR/CRP, thyroid function tests and anti-thyroid antibodies (anti-TPO, anti-thyroglobulin), and total IgE (low levels may predict anti-IgE/anti-FcepsilonRI autoimmune CSU). ASST or basophil histamine release assay can assess the autoimmune mechanism. Extensive allergy panels, complement levels, ANA, and imaging are not routinely indicated. Biopsy should be considered if wheals last more than 24 hours, are painful, or leave bruising, to rule out urticarial vasculitis.

Angioedema Without Urticaria

Bradykinin-mediated angioedema must be ruled out by checking C4 level (low in HAE even between attacks), C1-INH level and function, and C1q level (low in acquired C1-INH deficiency but normal in HAE). The medication list should be reviewed for ACE inhibitors, ARBs (rarely implicated), and DPP-4 inhibitors.

Urticarial Vasculitis

Urticarial vasculitis presents with wheals lasting more than 24 hours that leave residual purpura or hyperpigmentation. The wheals are painful or burning rather than pruritic. Biopsy shows leukocytoclastic vasculitis. Hypocomplementemic urticarial vasculitis syndrome (HUVS), characterized by anti-C1q antibodies, may overlap with SLE. Workup includes complement levels (C3, C4, CH50), ANA, anti-C1q, and hepatitis serologies.

Management

Acute Urticaria

The trigger should be identified and removed. Second-generation H1 antihistamines (cetirizine, loratadine, fexofenadine) are first-line. A short course of systemic corticosteroids may be needed for severe episodes. Epinephrine is used for anaphylaxis.

Chronic Spontaneous Urticaria (Step-Up Approach)

Step 1 is standard-dose second-generation H1 antihistamines (cetirizine 10 mg, fexofenadine 180 mg, or loratadine 10 mg daily), continued for at least 2 to 4 weeks before escalation. Step 2 is up-dosing antihistamines to up to 4 times the standard dose (for example, cetirizine 10 mg four times daily), which is off-label but supported by EAACI/GA2LEN guidelines; sedation may limit up-dosing. Step 3 adds omalizumab (anti-IgE) at 150 to 300 mg subcutaneously every 4 weeks. Omalizumab binds free IgE and downregulates FcepsilonRI on mast cells and basophils, is effective in approximately 65 to 70 percent of CSU patients (with fast responders within 1 to 2 weeks and slow responders at 12 to 16 weeks), has an excellent safety profile requiring no monitoring, but disease recurs upon discontinuation in most patients. Step 4 adds cyclosporine (3 to 5 mg/kg/day), effective in approximately 60 to 70 percent of omalizumab-refractory patients, with monitoring of blood pressure, renal function, and lipids. Other options with more limited evidence include dapsone, sulfasalazine, methotrexate, and mycophenolate.

Emerging Therapies

Emerging options include ligelizumab (a higher-affinity anti-IgE with mixed trial results), BTK inhibitors such as remibrutinib (targeting mast cell and basophil signaling), anti-KIT antibodies (reducing mast cell numbers), and anti-Siglec-8 antibodies (depleting eosinophils and inhibiting mast cells).

Adjunctive Measures

Known exacerbating factors (NSAIDs, alcohol, stress, heat) should be avoided. H2 antihistamines (famotidine) may offer modest additive benefit. Leukotriene receptor antagonists (montelukast) may help NSAID-sensitive patients. First-generation antihistamines at bedtime (hydroxyzine, doxepin) can help nocturnal symptoms.

Management of Bradykinin-Mediated Angioedema

For ACE inhibitor-induced angioedema, the ACE inhibitor must be discontinued (do not substitute an ARB initially). For hereditary angioedema, acute attacks are treated with C1-INH concentrate (plasma-derived or recombinant), icatibant (bradykinin B2 receptor antagonist), or ecallantide (kallikrein inhibitor). Prophylaxis uses lanadelumab (anti-kallikrein monoclonal antibody), berotralstat (oral kallikrein inhibitor), or C1-INH concentrate. Epinephrine and antihistamines are not effective in HAE.

Controversy: Optimal CSU Workup

There is ongoing debate over how extensively to evaluate CSU. Some advocate minimal workup (CBC, TSH, CRP only) while others recommend broader screening. Evidence does not support routine infection screening (H. pylori, hepatitis, parasites) in most populations. Autoimmune markers (ASST, basophil activation test) may guide therapy selection but are not widely available. The consensus is that workup should be guided by clinical features rather than being reflexive.

Controversy: When to Escalate Beyond Antihistamines

The timing of omalizumab initiation varies: some guidelines suggest 2 to 4 weeks of up-dosed antihistamines first, while others allow earlier use for severe disease. Cost and access barriers may delay escalation. Patient quality of life (UAS7 score, CU-Q2oL) should drive treatment decisions, and there is growing consensus that early escalation improves outcomes and reduces disease burden.

<image>Clinical photograph series showing: (A) acute urticaria with multiple annular and polycyclic wheals on the trunk, (B) dermographism elicited by stroking the skin with a tongue depressor, (C) angioedema of the lip showing asymmetric non-pitting swelling, (D) urticarial vasculitis with residual purpura remaining after wheal resolution. Show on multiple skin tones.</image>

<image>Pathophysiology diagram of chronic spontaneous urticaria showing mast cell activation pathways: IgE-mediated allergen cross-linking of FcepsilonRI, autoimmune IgG anti-FcepsilonRI and anti-IgE antibodies, and complement-mediated activation. Show released mediators (histamine, prostaglandins, leukotrienes, cytokines) and their effects on blood vessels (vasodilation, permeability leading to wheals) and sensory nerves (pruritus). Map therapeutic targets: antihistamines blocking H1 receptors, omalizumab binding free IgE, and cyclosporine suppressing T-cell help.</image>

<image>Step-up treatment algorithm for chronic spontaneous urticaria: Step 1 (standard-dose second-generation antihistamine) leading to Step 2 (up-dosed antihistamine, up to 4x) leading to Step 3 (add omalizumab) leading to Step 4 (add cyclosporine or alternative immunosuppressant). Include UAS7 score thresholds and recommended wait times between steps.</image>

Clinical Pearls

Individual urticarial wheals lasting more than 24 hours, leaving bruising, or associated with pain rather than itch should prompt biopsy to rule out urticarial vasculitis. Angioedema without urticaria should raise concern for bradykinin-mediated angioedema (HAE, ACE inhibitor-induced); antihistamines and epinephrine are ineffective in these conditions. Up-dosing second-generation antihistamines to 4 times the standard dose is safe and recommended by international guidelines before escalating to omalizumab. A low total IgE level in CSU may predict an autoimmune mechanism (type IIb) and possibly slower response to omalizumab. NSAIDs exacerbate urticaria in up to 30 percent of CSU patients via the COX-1 pathway; acetaminophen or selective COX-2 inhibitors are safer alternatives. Screen CSU patients for thyroid autoimmunity; treatment of thyroid disease may improve urticaria control in some cases.

References

• Zuberbier T, Abdul Latiff AH, Abuzakouk M, et al. The international EAACI/GA2LEN/EuroGuiDerm/APAAACI guideline for the definition, classification, diagnosis, and management of urticaria. Allergy. 2022;77(3):734-766.
• Maurer M, Rosen K, Hsieh HJ, et al. Omalizumab for the treatment of chronic idiopathic or spontaneous urticaria. N Engl J Med. 2013;368(10):924-935.
• Bernstein JA, et al. The diagnosis and management of acute and chronic urticaria: 2014 update. J Allergy Clin Immunol. 2014;133(5):1270-1277.
• Kolkhir P, Metz M, Altrichter S, Maurer M. Comorbidity of chronic spontaneous urticaria and autoimmune thyroid diseases. Allergy. 2017;72(9):1440-1460.

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