1. Cellulitis

3. Erysipelas

4. Cellulitis can involve any area of the body, lower extremity is most common.
Erysipelas is associated with marked swelling of the skin and does not involve subcutaneous tissues.
Risk factors:
Disruption of the cutaneous barrier
Venous or lymphatic compromise
Previous history of cellulitis

5. MICROBIOLOGY
Cellulitis in the majority of patients is caused by beta- hemolytic streptococci, including groups A, B, and, less often, C, and G.
Staphylococcus aureus is also common.

6. Differential Diagnosis
Contact dermatitis
Insect stings
Drug reactions
Foreign body reactions
Lymphedema
Gouty arthritis
Uncommonly: urticaria, lupus, sarcoidosis, lymphoma, leukemia, Paget disease, and panniculitis.

7. Treatment
The 2005 Infectious Diseases Society of America (IDSA) guideline:
penicillinase-resistant semisynthetic penicillin or a 1st generation cephalosporin (Cefazolin)
Vancomycin for those patients with severe infection particularly those infections associated with necrosis.

8. PCN allergy:
Clindamycin
Vancomycin
Oral therapy:
Cephalexin, Dicloxacillin,
Fluoroquinolones
Duration of therapy — The usual duration of antimicrobial therapy is 10 to 14 days.

9. Special Situations Fresh water - Aeromonas species
→Ciprofloxacin + Cefazolin
Salt water - Vibrio vulnificus
→Tetracyclines
Hot tub exposure - Pseudomonas aeruginosa
Cat bites - Pasteurella multocida
→penicillin + beta-lactamase inhibitor (Augmentin)