CU is immediate and resolves quickly. This distinguishes it from allergic CD, which develops hours to days after contact with the offending agent and lasts for days to weeks. Urticaria may be confused with other dermatologic diseases that can present in similar ways and are pruritic, including erythema multiforme, atopic dermatitis, insect bites, and drug eruptions.
Other signs that distinguish urticaria include the hallmark appearance, transient nature of the lesions, the intense pruritus, a lack of epidermal change, the presence of receding and advancing edges, and the complete blanching of lesions with pressure. Urticaria can be linear, annular, circular, or arcuate.
Patch testing identifies external allergens that produce a delayed reaction; it is usually used for patients with recurrent or chronic allergic CD who receive the greatest quality-of-life benefits from it. History regarding the time of onset distinguishes the two; patch testing is not required nor useful. Both CD and CU may potentially be treated with corticosteroids.
Learn more about allergic CD.
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Cite this: William James. Fast Five Quiz: Urticaria (Hives) - Medscape - Dec 12, 2022.