Acute Urticaria Workup

Updated: Sep 18, 2023
  • Author: Henry K Wong, MD, PhD; Chief Editor: Michael A Kaliner, MD  more...
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Approach Considerations

Acute urticaria is generally diagnosed based on a detailed patient history and physical examination (see Clinical Presentation), [2, 3, 4] and laboratory studies generally are not indicated. In pediatric cases, screening for streptococcal antigen may be indicated. [18] The patient's history and physical examination should direct any diagnostic studies. [44, 2, 45]

Imaging studies generally are not indicated unless a specific finding on clinical examination or history suggests an underlying etiology that may warrant further diagnostic studies. [46]

The 2022 EAACI/GA2LEN/EDF/WAO diagnosis guideline recommends using the urticaria activity score (UAS) proposed in the previous version of the guideline to measure disease severity and monitor treatment results in daily practice. The UAS assigns a score from 0 (no disease activity) to 3 (intense activity) for each of the 2 key urticaria symptoms, wheals and pruritus. The sum of the scores represents disease severity on a scale from 0 (minimum) to 6 (maximum). [5]


Skin Tests

Selected allergy tests can be performed if food allergy or stinging insect hypersensitivity is suspected. This process may be helpful for some cases of acute urticaria, but these studies are rarely helpful in the evaluation of chronic urticaria. [20] However, they may be needed to rule out an atopic component and label the urticaria as idiopathic.

Skin tests or radioallergosorbent assay test (RAST) (specific IgE) can be performed to detect hypersensitivity to a limited number of antibiotics. Testing for pollen or other inhalants is generally not helpful, unless a severe allergy may be causing the urticaria, such as a severe allergy to pollens, cats, or latex (these may manifest as contact urticaria).

Routine allergy testing with a large battery of screening tests is not recommended. A few research centers perform an autologous serum skin test, but it is currently not a well-established procedure.


Physical Challenge Tests

Physical urticaria can be confirmed with physical challenge tests. These involve the application of the suspected stimuli (heat, pressure, light, vibration, scratching [dermographism], cold [ice cube]) to the skin. Exercise testing can also be performed to diagnose cholinergic urticaria. Ice cube test findings are typically negative in patients with familial cold autoinflammatory syndrome. With the exception of testing for dermographism, these tests are usually performed only by specialty centers.


Skin Biopsy

A diagnostic skin biopsy is not helpful but should be considered if lesions do not resolve in patients suspected of having urticarial vasculitis (eg, in patients who present with features such as fever, painful lesions, arthralgia, elevated erythroid segmentation rate, lesions that last 24 hours or longer, or lesions that resolve with residual petechiae or purpura). [35, 47]


Histologic Findings

The histologic findings of acute urticaria are not dramatic. No epidermal change is present. Acute urticaria demonstrates intravascular margination of neutrophils. Later lesions demonstrate diapedesis of neutrophils through the vessel wall in the absence of karyorrhexis. Late lesions demonstrate intravascular, perivascular, and interstitial neutrophils with little to no karyorrhexis. A moderate number of eosinophils may be present. [48]