Antibiotic Treatment for Bacterial Dermatitis
Systemic antibiotics should be reserved exclusively for dermatitis with clear clinical evidence of bacterial infection—such as purulent exudate, pustules, or systemic signs—while topical mupirocin is appropriate for limited, superficial secondary infections. 1, 2
When to Use Antibiotics in Dermatitis
Clinical Indicators for Antibiotic Therapy
Antibiotics are NOT recommended for non-infected or merely colonized dermatitic skin, even though Staphylococcus aureus colonizes over 90% of atopic dermatitis lesions. 1 The key distinction is identifying frank bacterial infection versus colonization or inflammation:
Signs suggesting bacterial infection requiring antibiotics: 1
- Purulent exudate
- Pustules on examination
- Honey-colored crusting with weeping
- Systemic signs (fever, malaise)
- Rapidly spreading erythema
Signs that may be misleading: 1
- Simple crusting (can occur in active dermatitis without infection)
- Colonization alone (does not warrant treatment)
Topical Antibiotic Therapy
First-Line Topical Treatment
Mupirocin 2% ointment applied 3 times daily is the first-line topical antibiotic for limited, superficial secondary bacterial infections in dermatitis. 2, 3
- Efficacy: 71-93% clinical cure rates in infected dermatitis, with 94-100% pathogen eradication 3
- Duration: Typically 7 days, adjusted based on clinical response 2
- Indications for topical therapy: 2
- Limited number of lesions
- Superficial involvement only
- No systemic signs
- No high-risk comorbidities (diabetes, immunosuppression)
Critical Caveat on Topical Antibiotics
Long-term application of topical antibiotics is NOT recommended due to increased resistance risk and skin sensitization. 1 Colony counts return to baseline within days to weeks after discontinuation, and incomplete eradication promotes resistance. 1
Systemic Antibiotic Therapy
When to Escalate to Systemic Antibiotics
Systemic antibiotics are indicated when: 1, 2
- Infection is widespread (multiple lesions)
- Deeper tissue involvement is present
- Signs of systemic illness exist
- Patient has high-risk comorbidities (diabetes, immunosuppression)
- Infection involves high-risk areas (face, hands, genitals)
Specific Antibiotic Recommendations
For methicillin-susceptible S. aureus (MSSA)—the most common pathogen in infected dermatitis: 1, 4
- Flucloxacillin (first choice in many regions) 1
- Dicloxacillin 500 mg four times daily 4
- Cephalexin 500 mg four times daily 4
- Erythromycin (alternative for penicillin allergy) 1, 5
For methicillin-resistant S. aureus (MRSA): 4
- Trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily
- Doxycycline 100 mg twice daily
- Linezolid 600 mg twice daily (for severe cases)
For streptococcal infections: 1
- Phenoxymethylpenicillin if β-hemolytic streptococci isolated
- Minimum 10 days of therapy to prevent rheumatic fever 4
Duration and Monitoring
- Standard duration: 7-14 days based on clinical response 4
- Culture and sensitivity testing: Recommended for recurrent infections, treatment failures, or severe infections 1, 4
- Antibiotics should be given in addition to standard dermatitis treatment (topical corticosteroids or calcineurin inhibitors) 1
Special Consideration: Eczema Herpeticum
Eczema herpeticum is a dermatologic emergency requiring immediate systemic antiviral therapy with acyclovir. 1 This HSV superinfection historically carried 10-50% mortality when untreated, but mortality is now zero with prompt systemic antiviral treatment. 1 Earlier acyclovir initiation directly correlates with shorter hospital stays. 1
Common Pitfalls to Avoid
- Do not use antibiotics prophylactically for colonized but non-infected dermatitis—this promotes resistance without improving outcomes 1
- Do not use topical antibiotics long-term as maintenance therapy 1
- Do not confuse crusting alone with infection—look for purulent exudate and pustules 1
- Do not delay acyclovir if eczema herpeticum is suspected—this is time-sensitive 1