Cellulitis vs Erysipelas
Cellulitis and Erysipelas are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.
Cellulitis vs Erysipelas at a glance
- Cellulitis: Acute bacterial infection of the dermis and subcutaneous tissue, most often caused by beta-hemolytic streptococci or Staphylococcus aureus.
- Erysipelas: Superficial cellulitis with prominent lymphatic involvement, sharply demarcated borders, and a classic 'peau d'orange' appearance — almost always streptococcal.
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Side-by-side comparison
| Feature | Cellulitis | Erysipelas |
|---|---|---|
| At a glance | Acute bacterial infection of the dermis and subcutaneous tissue, most often caused by beta-hemolytic streptococci or Staphylococcus aureus. | Superficial cellulitis with prominent lymphatic involvement, sharply demarcated borders, and a classic 'peau d'orange' appearance — almost always streptococcal. |
| Classic presentation | Unilateral lower-leg cellulitis is extremely common; bilateral lower-leg 'cellulitis' is almost never cellulitis — consider stasis dermatitis, lipodermatosclerosis, or contact dermatitis.; Localized warmth, erythema, edema, tenderness — usually a single extremity; Spreading borders without sharp demarcation; Fever, chills, malaise in… | A sharply demarcated, raised, fiery red facial or leg plaque with a clear edge ('the lesion you can trace') and a high fever — classic erysipelas.; Abrupt onset of fever, chills, malaise — often precedes rash by hours; Localized burning pain and tenderness; Bright red, hot, swollen plaque with sharply raised border; Classic… |
| Workup / key labs | Clinical diagnosis. IDSA stratifies into mild, moderate, severe and purulent vs non-purulent for treatment selection.; CBC, BMP, lactate if systemic toxicity; Blood cultures only if severe sepsis, immunocompromise, water exposure, animal/human bites, or unusual organism suspected; Wound culture if purulent drainage or abscess (incise… | Clinical: sharply demarcated, raised, brightly erythematous, warm, tender plaque with systemic symptoms.; Clinical diagnosis — labs not routinely required; CBC, CRP, ESR if hospitalized or severe; Blood cultures yield in ~5% — only if systemic toxicity, immunocompromise, atypical presentation; ASO/anti-DNase B may support recent… |
| Imaging | Bedside ultrasound to differentiate cellulitis (cobblestoning) from abscess (anechoic collection); Plain films for foreign body, soft tissue gas (necrotizing infection), or osteomyelitis; CT/MRI if necrotizing fasciitis suspected (but do NOT delay surgical consultation for imaging) | Not required for typical presentations; Ultrasound to exclude abscess if purulence suspected |
| First-line treatment | Non-purulent cellulitis (likely beta-hemolytic strep):; • Mild outpatient: oral beta-lactam — cephalexin 500 mg PO QID, dicloxacillin 500 mg PO QID, or penicillin VK; • Moderate: IV cefazolin or ceftriaxone; • Severe (systemic toxicity, rapid progression): IV vancomycin + piperacillin-tazobactam pending evaluation for necrotizing… | Penicillin remains drug of choice — narrow spectrum, predictable streptococcal coverage:; • Oral: penicillin VK 500 mg PO QID or amoxicillin 500 mg PO TID × 5-10 days; • IV: penicillin G 1-2 million units IV q6h, or ceftriaxone 1 g IV daily; Cephalosporins or macrolides for penicillin-allergic patients (clindamycin or azithromycin);… |
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