Patients will be enrolled in a multi-center study to prospectively evaluate outcome after treatment for an uncomplicated skin abscess. All patients will receive incision and drainage and wound cultures. Patients will then be randomized to 1) placebo two tablets PO BID X 7 days or 2) bactrim DS (800/160) two tablets PO BID x 7 days. Patients will then return to the emergency department ED) at 48 hours and 7 for wound repacking and evaluation. The primary outcome is treatment failure rates at 7 days after incision and drainage. Patients who are clinically worsening or not improving after 48 hours will then be treated with additional antibiotics or admission if needed. Data will be analyzed both by initial randomization and intention to treat.

Inclusion Criteria:

• Inclusion criteria include all patients age 16 and older who present to the emergency department with a skin abscess that requires incision and drainage.

Exclusion Criteria:

• Exclusion criteria include patients with diabetes, HIV, cancer or other immunocompromised patients.
• Additionally, any patients who received antibiotics within one week of presentation or were hospitalized in previous month will be excluded to minimize potential confounding variables.
• Pregnant and breastfeeding patients will also be excluded due to possible safety concerns with antibiotic treatment.
• Patients with abscesses on face, perirectal, or perianal regions, abscesses with known tracks or fistulas to deeper structures, or abscesses requiring surgical drainage in an operating room are excluded.
• Patients with fever or evidence of systemic infection
• Finally, patients with sulfa allergy will be excluded.