Synopsis
Recognise non-purulent bacterial skin infection, grade severity, distinguish common mimics and prescribe safe narrow therapy while addressing portals of entry and recurrence.
- Cellulitis is a spreading infection of dermis and subcutaneous tissue; erysipelas is more superficial, raised and sharply demarcated.
- Typical findings are unilateral warmth, erythema, tenderness and swelling, sometimes with lymphangitis or systemic upset.
- Bilateral red legs are rarely bilateral cellulitis; venous stasis, lipodermatosclerosis and oedema are common mimics.
Key red flags
Pain out of proportion or rapidly advancing oedema suggests necrotising soft-tissue infection.
Fever, rigors, tachycardia, hypotension, delirium or reduced urine output indicates systemic involvement and possible sepsis.
Investigation priorities
Define extent, severity, portal of entry and a reproducible baseline for reassessment.
Management branches
Uncomplicated cellulitis is likely, physiology is stable and oral absorption and follow-up are reliable.
- Document the site, margin, pain, observations, portal of entry, allergy reaction, renal function and factors that alter organism risk.
- Give flucloxacillin 500 mg to 1 g orally four times daily for five to seven days when suitable, using a guideline-listed allergy alternative when needed.
Key medicines
FlucloxacillinGive 500 mg to 1 g orally four times daily for five to seven days for uncomplicated adult cellulitis; use intravenous dosing when severity requires admission.
ClarithromycinGive 500 mg orally twice daily for five to seven days when penicillin allergy makes flucloxacillin unsuitable.