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For further information, see CMDT PART 6-32: REACTIVE ERYTHEMAS

Key Features

Essentials of Diagnosis

  • Eruptions of evanescent wheals or hives with or without angioedema

  • Itching is intense, but very rarely, may be absent

  • Urticaria is divided into acute and chronic forms

  • Most incidents are acute and self-limited (1–2 weeks)

  • Chronic urticaria (lasting > 6 weeks) may have an autoimmune basis

General Considerations

  • Urticaria is defined as acute (< 6 weeks' duration) or chronic (> 6 weeks' duration)

  • Chronic urticaria is further divided into chronic spontaneous urticaria and chronic inducible urticaria

  • Chronic inducible urticaria is reproducibly triggered by specific exposures, such as

    • Cholinergic urticaria

    • Solar urticaria

    • Cold urticaria

    • Dermatographism

    • Delayed pressure urticaria

Clinical Findings

Symptoms and Signs

  • Hives or angioedema or both

  • Lesions are itchy red swellings of a few millimeters to many centimeters

  • The morphology of the lesions may vary over a period of minutes to hours

  • Individual lesions in true urticaria last < 24 h, and often only 2–4 h

  • Angioedema is involvement of deeper vessels, with swelling of the lips, eyelids, palms, soles, and genitalia in association with more typical lesions

  • Angioedema is no more likely than urticaria to be associated with systemic complications such as laryngeal edema or hypotension

  • In cholinergic urticaria, triggered by a rise in core body temperature (hot showers, exercise), wheals are 2–3 mm in diameter with a large surrounding red flare

Differential Diagnosis

  • True urticaria should be differentiated from diseases that present with similar lesions that are not true urticaria (eg, adult-onset Still disease, urticarial vasculitis, and cryopyrin associated periodic syndromes)

  • Vasculitis

  • Erythema multiforme

  • Contact dermatitis (eg, poison oak or ivy)

  • Cellulitis

Diagnosis

  • In general, a careful history and physical examination are helpful but extensive costly workups are not indicated

Laboratory Tests

  • Laboratory studies are generally not helpful in the evaluation of acute or chronic urticaria unless there are suggestive findings in the history and physical examination

  • A complete blood count with differential, erythrocyte sedimentation rate or C-reactive protein, thyroid-stimulating hormone, and liver chemistries may be appropriate for some patients with chronic urticaria

  • Functional ELISA test can detect patients with an autoimmune basis for their chronic urticaria

  • Some patients with chronic spontaneous urticaria demonstrate autoantibodies directed against mast cell IgE receptors

Diagnostic Procedures

  • In patients with individual lesions that persist past 24 h, a skin biopsy may confirm neutrophilic urticaria or urticarial vasculitis

Treatment

Medications

  • H1-antihistamines

    • Hydroxyzine, 10–25 mg orally two or three times daily or as a single nightly dose of 50–75 mg to reduce daytime sedation, is initial therapy

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