Cellulitis vs Erysipelas
How to tell Cellulitis and Erysipelas apart when a board question makes them look alike.
Cellulitis is deeper and ill-defined; erysipelas is superficial, raised, bright red, and sharply demarcated.
Side by side
Cellulitis is deeper dermal/subcutaneous infection with warmth, edema, tenderness, pink-red erythema, and poorly demarcated flat borders.
Erysipelas is more superficial upper dermal/lymphatic infection with bright red, raised, sharply demarcated borders, often on face or legs.
Bacterial invasion through skin barrier disruption spreads through dermis and subcutaneous tissue, commonly from streptococci or S. aureus.
Superficial streptococcal infection of upper dermis and lymphatics produces elevated, well-defined erythema.
Ill-defined spreading erythema, deeper edema, trauma/ulcer/tinea portal, and possible purulence support cellulitis.
Raised advancing edge, sharply demarcated bright erythema, lymphatic involvement, fever, and group A strep association support erysipelas.
The trap
Both are non-necrotizing skin infections, so border sharpness and depth are the fastest exam separator.
Watch it explained
The repair move
For non-necrotizing skin infection, inspect the lesion border, elevation, and depth in three steps: (1) BORDER and ELEVATION sharply demarcated, raised, palpable border that you can run your finger along equals erysipelas (a more superficial infection of the upper dermis and superficial lymphatics, classic on the face and lower extremities, almost always group A Strep, fevers can be high); poorly demarcated border that fades into normal skin equals cellulitis (deeper infection involving deep dermis and subcutaneous fat, more commonly streptococci or Staphylococcus aureus including MRSA); (2) DEPTH and PAIN both cause warmth, erythema, edema, tenderness; pain out of proportion to exam findings or rapid progression should prompt urgent evaluation for necrotizing fasciitis; (3) TREATMENT erysipelas: penicillin or amoxicillin (group A Strep); cellulitis: cephalexin or dicloxacillin for non-purulent; add MRSA coverage (TMP-SMX, doxycycline, clindamycin) for purulent cellulitis or abscess.
Try a free question
CoreA patient has a warm tender lower-leg plaque after tinea pedis with flat pink erythema and poorly demarcated edges. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Cellulitis. Warm tender skin infection with deeper, flat, poorly demarcated erythema supports cellulitis.
Why the other choices are tempting
- B. Erysipelas is raised, bright red, and sharply demarcated.
- C. Necrotizing fasciitis has severe pain/toxicity and deep necrosis signs.
- D. Herpes zoster causes dermatomal vesicles.
- E. Psoriasis causes chronic plaques with scale.
Flashcards
Tap a card to flip it.
What border supports cellulitis?
Poorly demarcated flat borders support cellulitis.
What border supports erysipelas?
Raised, sharply demarcated borders support erysipelas.
Quick answers
What is the fastest way to tell Cellulitis from Erysipelas?
Cellulitis is deeper and ill-defined; erysipelas is superficial, raised, bright red, and sharply demarcated.
What is the key clue for Cellulitis?
Cellulitis is deeper dermal/subcutaneous infection with warmth, edema, tenderness, pink-red erythema, and poorly demarcated flat borders.
What is the key clue for Erysipelas?
Erysipelas is more superficial upper dermal/lymphatic infection with bright red, raised, sharply demarcated borders, often on face or legs.
What is the common trap with Cellulitis vs Erysipelas?
Both are non-necrotizing skin infections, so border sharpness and depth are the fastest exam separator.