Pruritus, Urticaria, and Angioedema

Pruritus or itching (Table 9) is a dermal reaction to diverse stimuli, including light touch, vibration, wool fibers, and a number of chemical mediators. Histamine, released by mast cells is one of the most significant chemical mediators. Pruritus is a common symptom of primary skin diseases including allergic contact dermatitis. Less commonly it reflects a systemic reaction to drugs (e.g., NSAIDs, penicillin, and opioids) and other allergens.

Urticaria (Table 9) is a reaction to vasoactive substances (e.g., histamine) released by mast cells in the superficial dermis resulting in intradermal edema caused by capillary and venous vasodilation. The process could be an IgE-mediated type I hypersensitivity reaction; direct non-immune-mediated-activation of mast cells by drugs; drug-induced cyclooxygenase inhibition that activates mast cells by poorly understood mechanisms; or caused by stress and anxiety.

Angioedema (Table 9) is anaphylaxis of the subcutaneous tissues. It results from mast cell and basophil activation in the deeper dermis and subcutaneous tissues and is pathogenically related to urticaria which occurs at the epidermal-dermal junction. The causes of acute angioedema, which may be accompanied by pruritus and urticaria, include drugs and other allergens. Chronic angioedema is mostly idiopathic, rarely IgE mediated, and some cases are hereditary.

Table 9. Pruritus, Urticaria, and Angioedema.

Prevention:
  • Identify at-risk patient
    • Reduce stress
    • Do not prescribe COX-inhibitors
    • Ensure profound local anesthesia
      • Use local anesthetic agents containing a vasoconstrictor congruent with the patient’s functional capacity
Signs and symptoms:
  • Pruritus
    • Localized itching
    • Generalized itching
    • Maculopapular or urticarial rash
  • Urticaria
    • Migratory, well-circumscribed, erythematous pruritic wheals of the skin
      • The onset with contact or inhaled allergens is within minutes or hours following exposure
      • The onset with ingested allergens is within 48 hours
      • The onset with emotional stimuli is within seconds or minutes
    • Urticaria may be accompanied by angioedema
  • Angioedema
    • May be pruritic or non-pruritic and may be accompanied by urticaria
    • Local, diffuse painful swelling of the face, eyelids, lips, tongue, and extremities (back of hands)
    • Swelling of the tongue and pharyngeal and laryngeal edema may cause respiratory distress
      • Complete airway obstruction can occur
Emergency response:
  • Stop exposure precipitating agent
    • Pruritus
      • Generalized
        • Administer oral diphenhydramine (an H1-receptor antagonist)
          • 25 to 50 mg, four times daily until symptoms subside
      • Acute urticaria
        • Administer oral diphenhydramine (an H1-receptor antagonist)
          • 25 to 50 mg, four times daily until symptoms subside
        • Acute angioedema
          • Mild angioedema
            • Administer diphenhydramine (an H1-receptor antagonist)
              • 25 to 50 mg, four times daily until symptoms subside
          • Severe angioedema
            • Administer prednisone
              • 30 to 40 mg, by mouth, once a day, until symptoms subside
          • Pharyngeal or laryngeal edema with stridor and wheezing
            • Activate EMS
              • Immediately administer epinephrine 1:1000
                • Adult: epinephrine (EpiPen), 0.3 mg, IM (anterolateral thigh)
                • Child: epinephrine (EpiPen Jr), 0.15 mg, IM (anterolateral thigh)
Nota bene:
  • Signs of recovery: signs and symptoms subside
  • Signs of deterioration: progressive angioedema’ stridor, wheezing and other evidence of respiratory distress