Drug allergy and delabelling in children — formative SAQs

SAQ 1 (10 marks)

A 6-year-old girl is admitted with community-acquired pneumonia. She has carried a "penicillin allergy" label since age 2, when she developed a maculopapular rash on day 5 of amoxicillin given for a viral upper-respiratory infection. Her mother recalls the rash was widespread but that the child was otherwise well, and there was no swelling, breathing difficulty, blistering or mucosal involvement. The label has never been formally evaluated. She needs amoxicillin. [3]

Question: Outline the stepwise evaluation and management of this child's penicillin-allergy label, including history, risk stratification, the diagnostic pathway and the disposition. (10 marks) [10]

Model answer

Structured history (2 marks). Take a structured allergy history capturing the specific drug, dose, route and indication; the exact reaction and symptoms; the timing of onset relative to the doses; whether the drug was stopped and what happened; any co-illness (especially viral); previous tolerances and re-exposures; and family history. The history here — a morbilliform rash on day 5 of amoxicillin during a viral illness, with no systemic features — is low-risk and is the classic pattern of a false label. [3]

Risk stratification (2 marks). Apply a validated clinical decision rule. The PEN-FAST score, developed and validated by Trubiano and colleagues, stratifies risk from the history; a score under 3 identifies a low-risk patient suitable for direct oral challenge without prior skin testing. This child's remote, mild, non-systemic reaction gives her a low PEN-FAST score. Actively seek the history red flags (anaphylaxis, blistering, mucosal involvement, multi-organ disease) that would instead mandate specialist referral and never-challenge; none are present here. [2] [10]

Diagnostic pathway (3 marks). Proceed to a direct oral amoxicillin challenge under medical observation, with rescue medication and anaphylaxis capacity available, for a defined observation period. The PALACE randomised trial by Copaescu and colleagues showed that a PEN-FAST-guided direct oral challenge was non-inferior to skin testing for low-risk penicillin allergy and more efficient, and a meta-analysis confirmed direct drug provocation is safe in selected children with beta-lactam hypersensitivity. If she tolerates the challenge, the label is false; if she reacts, the label is confirmed and she avoids the drug. [1] [6]

Disposition (3 marks). On tolerance, remove the label and document it everywhere — the electronic medical record, pharmacy record, MedicAlert, the family-held record and the medication list; counsel the family verbally and in writing; and communicate with the general practitioner. A label that survives in one record resurfaces and the harm recurs, so complete cross-system documentation is part of the treatment. The systems-level gain is antibiotic stewardship: restoring first-line amoxicillin avoids broader-spectrum, more toxic alternatives. [10] [8]

SAQ 2 (10 marks)

Question: (a) Describe the recognition and immediate management of drug-induced anaphylaxis in a child. (b) Identify the severe delayed drug reactions that are absolute contraindications to re-challenge, and explain why these children are never delabelled by direct challenge. (10 marks) [7]

Model answer

(a) Recognition and immediate management of anaphylaxis (5 marks). Anaphylaxis presents within minutes to one hour of drug exposure with airway, breathing or circulation compromise — stridor, wheeze, respiratory distress, hypotension or collapse — often with urticaria, angioedema and gastrointestinal symptoms. Recognise it and treat immediately with intramuscular adrenaline (epinephrine) at 0.01 mg/kg (0.01 mL/kg of 1:1000, or 10 microgram/kg) into the anterolateral thigh, repeated every 5 minutes as needed; stop the drug, secure the airway, give oxygen, position supine and give intravenous fluids. Antihistamine and corticosteroid are adjuncts for urticaria, never a substitute for adrenaline when the airway or circulation is involved. The European Anaphylaxis Registry confirms drug-induced anaphylaxis is a major cause in children. Arrange definitive allergy evaluation once the acute episode settles. [7]

(b) Severe delayed reactions and why they are never re-challenged (5 marks). The severe delayed reactions are Stevens-Johnson syndrome and toxic epidermal necrolysis (blistering, target lesions, skin pain, mucosal involvement), DRESS (rash, fever, lymphadenopathy, eosinophilia, organ dysfunction 2–8 weeks after exposure) and acute generalised exanthematous pustulosis (sterile pustules with fever). These are absolute contraindications to re-challenge because re-exposure can be fatal. They are never part of any delabelling pathway and never challenged directly. These children need immediate cessation of the culprit drug, supportive and specialist management as the syndrome demands, and referral to specialist allergy services for definitive documentation and counselling on avoidance of the culprit and structurally related drugs. The EAACI beta-lactam position paper sets out this framework. The contrast with the low-risk label is the whole point: low-risk, unverified labels are challenged and delabelled; severe verified reactions are documented and avoided for life. [4]