Cellulitis

Audience: Patients and providers
Status: Clinical guide · patient + provider
Last updated: 2026-03-27

1. Clinical overview

Cellulitis is an acute bacterial skin and soft tissue infection that usually involves erythema, warmth, tenderness, and swelling, with treatment driven by severity, purulence, and host risk factors.

2. Common causes and risk factors

Beta-hemolytic streptococci are common in non-purulent disease.
Staphylococcus aureus, including MRSA, is more relevant in purulent infection or selected exposure patterns.
Skin breaks, edema, tinea pedis, diabetes, obesity, and venous or lymphatic disease increase recurrence risk.

3. Typical symptoms

Expanding erythema, warmth, tenderness, swelling, and sometimes fever or malaise.

4. Diagnosis and evaluation

Distinguish cellulitis from venous stasis dermatitis, gout, DVT, abscess, and contact reactions.
Check for purulence, fluctuance, bullae, necrosis, and systemic toxicity.
Identify portal of entry and modifiable recurrence factors such as interdigital fungal disease or chronic edema.

5. Treatment (non-pharmacologic)

Elevate the affected extremity and optimize wound/skin care.
Treat edema and skin barrier problems to reduce recurrence.
Mark borders when useful to judge progression over 24 to 48 hours.

6. Treatment (pharmacologic)

Mild non-purulent infection often responds to cephalexin, dicloxacillin, or amoxicillin in the right streptococcal-predominant setting.
Purulent disease or MRSA-risk infection may require trimethoprim/sulfamethoxazole, doxycycline, or clindamycin plus drainage when needed.
IV therapy may involve cefazolin, ceftriaxone, vancomycin, or broader regimens depending on toxicity, rapid progression, and host risk.

7. Monitoring and follow-up

Expect early improvement in pain, fever, and spread within 24 to 72 hours.
Reassess if erythema continues to expand, systemic symptoms develop, or adherence/tolerance is poor.

8. Practical counseling points

Redness can fade slowly even after appropriate therapy starts.
Review adherence, limb elevation, and warning signs clearly.
Reinforce foot care and skin care in diabetes or chronic edema.

9. Red flags and escalation

Escalate urgently for hypotension, severe pain out of proportion, crepitus, bullae, necrosis, or concern for necrotizing infection.
Reevaluate the diagnosis if there is no meaningful improvement in the expected timeframe.

10. Guideline references

IDSA skin and soft tissue infection guideline.
CDC antibiotic stewardship resources.
Diabetes foot-care guidance when lower-extremity risk is present.

Note: Educational guide only; not a substitute for individualized medical care.