Cellulitis
Also called skin and soft tissue infection
Bacterial infection of deep dermis and subcutaneous fat: a warm, tender, poorly demarcated, spreading unilateral erythema, usually on a leg, often with fever and a portal of entry.
How it looks
A poorly demarcated, warm, tender, oedematous erythematous area over the lower leg, spreading proximally, with a fissured interdigital web space as the likely portal.
Rose is the lesion, grey the pattern the lesions make, green where on the body it lives.
Across skin tones
Erythema is easy to miss in deeply pigmented skin, rely on warmth, tenderness, swelling, and shiny skin; compare with the other limb and mark the border to track spread.
Don't miss
Pain out of proportion, rapid progression, bullae, crepitus, or anaesthetic skin is necrotising fasciitis until surgically proven otherwise, this is a call for the surgeon, not a bigger antibiotic.
Symptoms & course
- Pain and tenderness
- Fever and malaise
- Rapid progression over hours to days
Diagnostic approach
- Clinical diagnosis; mark the border and reassess
- Blood cultures if febrile/septic
- Ultrasound if abscess suspected
Differential, and how to separate them
- Contact dermatitis
Favours it: Itch, vesicles, exposure shape, afebrile
Against it: Cellulitis is painful, warm, and systemic
Management principles
- Antibiotics covering streptococci and S. aureus per local guidance
- Elevate the limb; treat the portal (tinea pedis, ulcers)
- Escalate urgently if pain is out of proportion or the patient is toxic
Clinical pearl: Bilateral 'cellulitis' is almost always stasis dermatitis, cellulitis is overwhelmingly unilateral.
Clinical pearl: Look between the toes: the fungal portal of entry is the most treatable recurrence factor.
Keep going
Try the case: One red legCompare with Contact dermatitisBack to the Atlas