Post-Operative Hives and Itching at 1 Week

Immediate Clinical Assessment

• The presentation of hives and itching at 1 week post-surgery suggests either a delayed drug hypersensitivity reaction to perioperative medications or another cause, and is not consistent with immediate perioperative anaphylaxis 1, 2

Treatment Algorithm

• The American College of Cardiology is not mentioned, however, the guideline recommends initiating second-generation non-sedating H1-antihistamines (cetirizine, loratadine, fexofenadine, or desloratadine) at standard doses as first-line therapy for hives and itching developing 1 week post-operatively 1
• If symptoms persist beyond 48-72 hours, consider adding H2-antihistamines (famotidine or ranitidine) for generalized pruritus, though evidence is limited 1

Critical Differential Diagnoses to Exclude

• NSAID hypersensitivity can present as delayed urticaria and should prompt avoidance of all NSAIDs until allergy testing is completed 2
• Opioid-induced itching typically occurs immediately post-operatively, but residual effects can persist, and if opioid-related and persistent, consider naltrexone as first-line treatment, or alternatives like ondansetron, mirtazapine, or gabapentin 1

When to Refer for Allergy Investigation

• Mandatory referral criteria include symptoms persisting beyond 6 weeks, recurrent episodes with subsequent medication exposures, suspected NSAID or antibiotic hypersensitivity requiring future surgical procedures, and any associated angioedema or systemic symptoms 2, 3
• Allergy workup should include a detailed chronological narrative of all perioperative exposures, serum tryptase levels, and skin prick testing and specific IgE testing for suspected culprit drugs 2, 3

Important Caveats

• At 1 week post-surgery, this is not an immediate perioperative allergic reaction requiring epinephrine, and epinephrine is only indicated for acute anaphylaxis with multi-organ involvement (Grade II-IV reactions) 3, 4, 5
• Do not dismiss paracetamol/acetaminophen as "safe", as it can cause significant histamine release and cross-reactive NSAID hypersensitivity 2
• Do not rely solely on antihistamines if symptoms worsen or systemic features develop, and reassess for evolving anaphylaxis 1, 5
• Do not continue suspected culprit medications without allergy clearance 2