Recommended Antibiotics for Mild Cellulitis
For mild, non-purulent cellulitis without systemic signs of infection, prescribe oral antibiotics targeting streptococci: penicillin, amoxicillin, or cephalexin (such as cefalexin 500mg four times daily) for 5 days. 1
First-Line Treatment Algorithm
The IDSA guidelines 1 provide clear direction based on clinical presentation:
Typical mild cellulitis (no systemic signs): Use anti-streptococcal agents only
- Penicillin VK
- Amoxicillin
- Cephalexin (cefalexin)
Duration: 5 days is sufficient, extending only if no improvement 1
This streptococcal-focused approach is supported by recent evidence showing that β-hemolytic streptococci and methicillin-sensitive Staphylococcus aureus cause the majority of uncomplicated, non-purulent cellulitis 2. Importantly, MRSA coverage is NOT recommended for typical non-purulent cellulitis, even with rising community-acquired MRSA rates 2.
When to Broaden Coverage
Add MRSA-active antibiotics (trimethoprim-sulfamethoxazole, clindamycin, or doxycycline) ONLY if specific risk factors are present 1:
- Purulent drainage
- Penetrating trauma
- Injection drug use
- Known MRSA colonization
- MRSA infection elsewhere on body
- Systemic inflammatory response syndrome (SIRS)
In MRSA-prevalent areas, trimethoprim-sulfamethoxazole showed 91% success rates versus 74% for cephalexin 3, but this study included patients who may have had unrecognized purulent features.
Critical Practice Points
Oral antibiotics are as effective as IV antibiotics for uncomplicated cellulitis 4. A randomized trial demonstrated non-inferiority of oral cefalexin compared to IV cefazolin, with oral therapy actually showing faster resolution (1.29 vs 1.78 days to cessation of progression) 4.
Common pitfall: Overprescribing broad-spectrum antibiotics. The guideline explicitly states that typical cellulitis requires only streptococcal coverage 1. Reserve broader agents for the specific risk factors listed above.
Essential Adjunctive Measures
Beyond antibiotics 1:
- Elevate the affected limb
- Examine interdigital toe spaces for tinea pedis—treating fungal infection reduces recurrence risk
- Address underlying edema or skin conditions
The evidence strongly supports narrow-spectrum, short-duration oral therapy for mild cellulitis, reserving broader coverage and IV therapy for complicated cases with specific risk factors.