Warm, erythematous, tender spreading skin
ABCDE
Mark border; antibiotics; exclude necrotising infection (urgent surgery if suspected).
Non-purulent, sensitive → cefazolin/nafcillin/oxacillin (oral cephalexin/dicloxacillin)
Purulent / MRSA risk → I&D + TMP-SMX / clindamycin / doxycycline (IV vancomycin/linezolid if severe)
Necrotizing (pain out of proportion, crepitus) → emergent surgical debridement
Order set
- Mark border
- FBC, CRP
- Blood cultures if systemic
- Antibiotics
- Assess for abscess
Criteria
AdmitSystemic features, rapid spread, comorbidity
ICUNecrotising infection, septic shock
DischargeErythema regressing, afebrile, oral antibiotics, follow-up marked
Clinical detail — differentials, red flags, pitfalls, disposition
Red flags
- Pain out of proportion/crepitus (nec fasc)
- Sepsis
- Rapid spread
Differentials
- DVT
- Necrotising fasciitis
- Stasis dermatitis
- Gout
Common mistakes
- Missing necrotising infection
- Not draining abscess
- Prolonged courses — typical non-purulent cellulitis needs only 5 days; extend only if not improving (IDSA 2014)
Disposition & follow-up
Antibiotics ± drainage; surgery for necrotising.
Discharge package
MedicationsComplete antibiotics
Follow-upRecheck if not improving
LifestyleSkin/foot care, treat tinea/oedema
Warning symptomsSpreading redness, fever, blistering, severe pain
💊 Treatment detail — doses & preparation
Flucloxacillinanti-staph penicillin
Dose2 g IV q6h (severe cellulitis/osteomyelitis); 500 mg–1 g PO QID step-down
PreparationIV 2 g in 50 mL NS over 30 min
MonitorLFTs (cholestatic hepatitis), Na⁺ load
Clindamycinlincosamide
Dose600–900 mg IV q8h (MRSA cellulitis/toxin suppression); 300–450 mg PO QID
PreparationIV 600 mg in 50 mL over 30 min
MonitorC. diff risk, rash
Cephalexin (step-down)oral
Dose500 mg–1 g PO QID ×5–10 d
Preparation250/500 mg capsules
MonitorMark the erythema edge to track spread
📖 IDSA Skin & Soft TissueReviewed July 2026