Treatment for Penicillin Allergy Skin Rash
For a suspected allergic reaction to penicillin causing a skin rash, immediately discontinue the penicillin, administer antihistamines for symptom relief, and consider short-term corticosteroids for moderate to severe reactions. 1, 2
Initial Assessment and Management
Immediate Steps:
- Stop the penicillin immediately 2
- Classify the reaction based on timing and severity:
- Immediate reactions (<1 hour): urticaria, angioedema, anaphylaxis
- Accelerated reactions (1-72 hours): urticaria, maculopapular rashes
- Late reactions (>72 hours): skin rashes, erythema multiforme 3
Treatment Based on Severity:
For Mild to Moderate Skin Rash:
- Oral antihistamines (H1 blockers like cetirizine or diphenhydramine)
- Topical corticosteroids for localized reactions
- Adequate hydration and monitoring
For Severe Reactions:
- Epinephrine for anaphylactic symptoms
- Systemic corticosteroids (oral prednisone or IV methylprednisolone)
- Oxygen and airway management if respiratory symptoms present
- IV fluids as needed 2
Documentation and Future Management
Document in Medical Record:
- Specific penicillin used
- Timing of reaction after administration
- Detailed description of skin manifestations
- Treatment administered and response
Cross-Reactivity Considerations:
For immediate-type reactions:
- Avoid all penicillins
- Avoid cephalosporins with similar side chains to the culprit penicillin
- Monobactams and carbapenems can generally be used safely 3
For delayed-type non-severe reactions:
- Avoid the culprit penicillin and those with similar side chains
- Cephalosporins with dissimilar side chains can be used
- Monobactams and carbapenems are generally safe options 3
Future Antibiotic Use
Alternative Antibiotics:
- For patients with non-severe reactions:
- Cephalosporins with dissimilar side chains to penicillins
- Aztreonam (except with ceftazidime allergy)
- Carbapenems (low cross-reactivity rate of 0.87%) 1
Allergy Testing Recommendations:
- Skin testing should be considered before future penicillin use, especially for reactions that occurred less than 5 years ago
- Testing should include major determinants (Penicilloyl-poly-lisina) and minor determinants (Penicillin G) 1
- Even with negative tests, administer first dose in a controlled environment due to small risk (3-10%) of allergic reactions 1
Special Considerations
For Life-Threatening Infections Requiring Penicillin:
- Consider desensitization protocol under specialist supervision
- Oral desensitization starting with minimal doses (e.g., 100 units of penicillin G) and doubling every 15 minutes has shown success in patients with confirmed penicillin allergy 4
For Patients with Questionable Penicillin Allergy:
- Only about 10% of reported penicillin allergies can be confirmed with testing 5
- Consider risk stratification using tools like the PEN-FAST algorithm 1
- Low-risk patients (reactions >5 years ago) may be candidates for supervised challenge 1
Pitfalls to Avoid
- Don't continue penicillin in patients with confirmed allergic reactions
- Don't assume all beta-lactams are contraindicated in penicillin-allergic patients
- Don't fail to distinguish between true allergic reactions and side effects (e.g., nausea, diarrhea)
- Don't overlook the possibility of C. difficile infection, which can occur with antibiotic use and cause diarrhea 2