Inclusion Criteria:

1. Adult >= 18 years
2. Confirmed cellulitis according to the following definition: a) soft-tissue erythema of recent onset (within one week); b) infectious in origin; c) at least one of the following: warmth, fever, lymphangitis, induration, ulceration, pain

Exclusion Criteria:

1. Facial cellulitis
2. Current use of any antibiotic
3. Infection has been previously treated
4. Sulfa allergy
5. History of severe allergic reaction to penicillin
6. History of G6PD deficiency
7. Taking coumadin (warfarin), methotrexate, cisapride, or dofetilide
8. Patient has been diagnosed with renal insufficiency
9. History of diabetes mellitus
10. Cellulitis associated with marine or freshwater injury, or animal or human bite (Insect bites are okay for this study).
11. Pregnancy and/or Breast feeding
12. Admission to the hospital
13. Abscess yielding > 1 cc of pus
14. Cellulitis involves an indwelling vascular, enteric, or urinary catheter
15. Immunocompromise of any etiology
16. Known megaloblastic anemia due to folate deficiency
17. Cellulitis complicated by underlying peripheral vascular disease