At what age can we perform skin testing on a child for a medication allergy, such as penicillin?

Penicillin Skin Testing in Children: Age and Safety Considerations

Direct Answer

Penicillin skin testing can be safely performed in children of any age, including infants and neonates, when clinically indicated. There is no specific minimum age requirement for penicillin skin testing in pediatric patients 1.

Clinical Context and Evidence

No Age Restrictions

• CDC guidelines from 1993 through 2002 consistently state that skin testing "may be helpful in some patients and settings" for children requiring treatment for conditions like congenital syphilis, without specifying any age limitations 1
• These guidelines explicitly discuss penicillin allergy management in infants and children after the newborn period, indicating skin testing is appropriate across all pediatric age groups 1

Safety Profile in Children

• A large study of 778 children under 18 years demonstrated that penicillin skin testing is safe with zero adverse reactions observed during testing 2
• Another study of 191 pediatric patients (median age 6.83 years) confirmed that "none of our patients experienced immediate or delayed systemic and/or local reactions" to skin tests 3
• Even routine elective skin testing in 240 children and adolescents showed the procedure is "safe, highly predictive, nonsensitizing" when performed by experienced physicians 4

Modern Approach: Consider Direct Challenge Instead

For Low-Risk Pediatric Reactions

The 2022 Drug Allergy Practice Parameter strongly recommends against routine penicillin skin testing before direct amoxicillin challenge in children with benign cutaneous reactions (such as maculopapular rash or urticaria without systemic symptoms) 1

Criteria for Direct Challenge (No Skin Testing Needed):

• Past reaction was maculopapular exanthem or urticarial eruption 1
• No systemic symptoms (no respiratory or cardiovascular symptoms) 1
• No blistering, exfoliation, or angioedema 1
• No history of anaphylaxis 1

Rationale:

• Only 1.98% of children reporting penicillin allergy are truly allergic when properly tested 5
• Aminopenicillins cause benign delayed rashes in <7% of children, often related to concurrent viral infections rather than true allergy 1
• Direct challenge reaction rates are only 5-10% and generally mild 1

When Skin Testing Remains Appropriate

Skin testing should still be performed in children with:

• History of anaphylaxis (though one study showed only 82.4% NPV in this group) 6
• High-risk features: respiratory symptoms, cardiovascular symptoms, or severe cutaneous reactions 1
• Parental anxiety or clinician preference despite low-risk history 1
• Situations where penicillin is absolutely required (e.g., neurosyphilis, congenital syphilis) and desensitization planning is needed 1

Testing Methodology Considerations

Available Reagents Matter

• Full battery testing (major determinant Pre-Pen plus minor determinants) identifies 90-97% of allergic patients 1
• Testing with penicillin G alone (when Pre-Pen unavailable) has shown 95.2% negative predictive value in children, though this drops to 82.4% for those with anaphylaxis history 6
• The 2022 guidelines note that Pre-Pen is not FDA-indicated for pediatric use, yet multiple studies demonstrate safety and efficacy 2

Important Caveats

• Children are more likely to have positive skin tests (8.5-8.75%) compared to adults (3.6%), though most are still not truly allergic 2, 4
• Skin testing has high negative predictive value (92.2-95.2%) but drug provocation testing remains the gold standard 6, 3
• 3.8-4.8% of children with negative skin tests may still react to oral challenge, typically with mild reactions 2, 6

Practical Algorithm

1. Assess reaction history: Determine if low-risk (isolated rash/urticaria >5 years ago) or high-risk (anaphylaxis, systemic symptoms, severe cutaneous reactions)
2. For low-risk pediatric patients: Proceed directly to supervised amoxicillin challenge without skin testing 1
3. For high-risk patients or when penicillin is essential: Perform skin testing at any age, with appropriate monitoring and resuscitation equipment available 1, 2
4. If skin testing negative: Proceed to graded oral challenge 6, 3
5. If skin testing positive: Consider desensitization if penicillin is required 1