Micro & Immunology · patient case question
Which of his findings is the most specific sign of an allergic reaction?
Patient case: Rash After Local Anesthetic in a Child
Patient: 10-year-old male
Chief Complaint: Restorative treatment on two mandibular molars.
Background: Healthy, no known allergies, no previous dental treatment requiring anesthesia. Immunizations current.
Medications: None
Vital Signs: Baseline: BP 100/62 mmHg · HR 86 bpm · RR 18 · T 98.4°F
Findings: Twenty minutes after administration of 2% lidocaine with 1:100,000 epinephrine, he develops a generalized raised urticarial rash over the trunk and arms, accompanied by nausea, one episode of vomiting, and loose stools. Mild expiratory wheeze is audible. Airway is patent, phonation is normal, and blood pressure remains stable at 98/60 mmHg.
Show answer and explanation
Correct answer: A. Urticarial rash
- A. Correct. Urticaria — raised, pruritic, blanching wheals — is the direct visible consequence of mast cell histamine release increasing vascular permeability. It is the most specific of the findings listed for an allergic mechanism.
- B. Incorrect. Nausea is entirely non-specific. It accompanies vasovagal syncope, anxiety, and many drug effects with no immune basis at all.
- C. Incorrect. Diarrhea is part of the gastrointestinal component of anaphylaxis, but taken alone it does not distinguish an allergic reaction from gastroenteritis or an anxiety response.
- D. Incorrect. Vomiting occurs in an allergic reaction but occurs just as readily with anxiety, pain, and vasovagal episodes.
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