How do you differentiate cellulitis from erysipelas and what are the initial management principles?

• A. Erysipelas has poorly defined margins involving the deep dermis; cellulitis has well-demarcated margins.
• B. Erysipelas has well-demarcated margins involving the superficial dermis; cellulitis is less sharply demarcated; as such, initiate antibiotics covering streptococci and Staph.
• C. Erysipelas is treated with antifungals.
• D. Cellulitis always requires surgical drainage.

Answer: (B)

The main idea is telling apart erysipelas from cellulitis by how deep the infection goes and how clearly the border can be seen. Erysipelas affects the superficial dermis and lymphatic channels, so it typically presents as a bright red, raised plaque with well-defined, sharp borders. Cellulitis involves deeper layers of skin (the dermis and subcutaneous tissue), and its edges are often ill-defined, blending into surrounding tissue.

For initial management, start antibiotics that cover the common pathogens for these skin infections, which include streptococci and Staphylococcus aureus. In practice, this means choosing agents that address both organisms because you can’t reliably rule out Staph involvement, and purulent cases or MRSA risk may require broader coverage. If the infection is nonpurulent and mild, penicillin-class or first-generation cephalosporins that focus on streptococci can be appropriate; if there is purulence, systemic signs, or risk factors for MRSA, add coverage for Staphylococcus as well. Antifungal treatments are not indicated for bacterial erysipelas or cellulitis, and surgical drainage is not routinely required for cellulitis unless there is an abscess or another focal source of infection.

In short, well-demarcated, superficial involvement points toward erysipelas, ill-defined borders toward cellulitis, and initial care should prioritize antibiotics that cover both streptococci and Staphylococcus while reassessing the need for escalation to IV therapy or imaging based on severity and response.