Wheal

Background

• In urticaria (hives), both wheals and angioedema are present. Wheals result from localized edema of upper dermis, while angioedema results from edema of lower dermal and subcutaneous tissues
• Mast cell and basophil activation involving the release of vasoactive substances
• Broad differential diagnosis of etiologies
  • Sometimes iatrogenic; for example, skin wheals from intradermal lidocaine infiltration, allergy skin prick test, tuberculin skin test

Clinical Features

• Papules that are well-circumscribed but irregular, pruritic, and often with a pale center and red flare on the borders
• Transient duration, usually hours, with spontaneous self-resolution
• If related to anaphylaxis or allergy, may also involve other systems such as respiratory, circulatory, GI

Urticarial wheal

Differential Diagnosis

• Anaphylaxis
• Acute allergic reaction
• Contrast induced allergic reaction
• Acute transfusion reaction
• Chronic urticaria
• Dermatographism
• Cold urticaria

Evaluation

• Clinical diagnosis
  • Take a thorough history to assess for precipitating factors, including recent foods, travel, medications/treatments, insect bites/stings, autoimmune disease, viral infections, anaphylaxis history, etc
  • Check for association with overlying objects such as watches, jewelry clothing, bands, etc

Management

• If any suspicion of anaphylaxis, treat with IM epinephrine
• 2nd gen H1 antihistamines are effective; if ineffective, consider corticosteroids and H2 antihistamines
• Avoid any causative agent or medications if identified, and treat the underlying illness

Disposition

• Observe in ED for 4-6 hours until symptoms improve; utilize clinical gestalt
• If anaphylactic picture, after observation discharge with anaphylaxis emergency plan and epipen

See Also

• Angioedema
• Anaphylaxis
• Acute allergic reaction

References

Dermatology