skip to main content
ukmla 2026

Cellulitis and Erysipelas

Acute bacterial infection of skin and subcutaneous tissues — most commonly group A Streptococcus and S. aureus

Review date
reviewed 2026-04-05
Reading time
5 min read
Author
Dr Kola Tytler MBBS CertHE MBA MSt MRCGP
Dermatologycommonacute
On this page
Condition details
Dermatology
common
5 min read
reviewed 2026-04-05
practice ukmla questions →

About This Page

This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.

Key points

  • Cellulitis: poorly demarcated, deeper. Erysipelas: well-demarcated, raised border, more superficial
  • Commonest organisms: group A Streptococcus and Staphylococcus aureus
  • First-line: flucloxacillin 500 mg-1 g QDS for 5-7 days. Pen allergy: clarithromycin or doxycycline
  • Draw around edge with skin marker to track progression
  • Recurrent (>=2 in 12 months): prophylactic phenoxymethylpenicillin 250 mg BD

Overview

Cellulitis is an acute bacterial infection of the dermis and subcutaneous tissue with poorly demarcated borders. Erysipelas is a more superficial form with a well-demarcated, raised border. Both are commonly caused by group A beta-haemolytic streptococcus and S. aureus. Entry points include skin breaks, tinea pedis, ulcers, eczema, and insect bites.

Epidemiology

Accounts for 2-3% of hospital admissions. Lower limbs affected in ~70-80%. Risk factors: lymphoedema, obesity, venous insufficiency, tinea pedis, previous cellulitis, diabetes, immunosuppression, IV drug use. Recurrence rate ~30% at 3 years.

Clinical Features

Symptoms
Painful, warm, erythematous, swollen area — usually unilateral
Systemic symptoms: fever, malaise, rigors
Preceding skin break: wound, bite, tinea pedis
Rapid spread with dusky discolouration and severe pain (necrotising fasciitis)
Pain out of proportion to clinical signs
Crepitus on palpation
Signs
Erythema, warmth, swelling, tenderness — poorly demarcated (cellulitis)
Well-demarcated raised peau d'orange border (erysipelas)
Regional lymphadenopathy
Bullae/haemorrhagic bullae in severe cases
Periorbital involvement (risk of orbital cellulitis)

Investigations

First-line
Clinical diagnosisMark edge with skin marker to monitor. Blood tests if systemically unwell
Blood tests if febrileFBC, CRP, U&E, blood cultures
Second-line
Skin swabOnly if broken skin — MC&S for antibiotic guidance
Specialist
Duplex ultrasoundIf DVT differential — cellulitis and DVT can coexist
CT/MRIIf necrotising fasciitis suspected — should not delay surgical review

Management

NICE NG141 (Cellulitis and erysipelas), 2019
1
General measures
  • Mark edge with skin marker
  • Rest and elevate affected limb
  • Analgesia
  • Treat predisposing cause (tinea pedis, eczema)
2
Oral antibiotics (mild-moderate)
  • Flucloxacillin 500 mg QDS for 5-7 days
  • Pen allergy: clarithromycin 500 mg BD or doxycycline 200 mg then 100 mg OD
  • Facial: co-amoxiclav 500/125 mg TDS
3
IV antibiotics (severe/Eron III-IV)
  • IV flucloxacillin 1-2 g QDS
  • MRSA risk: IV vancomycin or teicoplanin
  • Step down to oral when improving
4
Preventing recurrence
  • Treat predisposing factors
  • If >=2 episodes in 12 months: prophylactic phenoxymethylpenicillin 250 mg BD
  • Review prophylaxis every 6 months

Complications

  • Abscess: May require I&D
  • Necrotising fasciitis: Pain out of proportion, rapid spread — emergency surgical debridement
  • Sepsis: Manage per Sepsis Six
  • Recurrence: ~30% at 3 years
  • Lymphoedema: Recurrent episodes damage lymphatics
UKMLA Exam Tips
  • 1Cellulitis is almost always UNILATERAL — bilateral red legs = venous eczema
  • 2Erysipelas: WELL-DEMARCATED raised border. Cellulitis: POORLY demarcated
  • 3Mark the edge with a pen — essential for monitoring
  • 4Pain out of proportion + rapid spread = think necrotising fasciitis
  • 5Always check between toes for tinea pedis as entry point

Put your reading into practice

Checking available topic practice…

Choose UKMLA questions from the existing bank. General exam practice covers your selected topics; it is not filtered to this article. Your usual question-bank access applies.

Choose UKMLA practice

After your session, return to this section to revisit the reading and choose your next review.

regional clinical guidance

Cellulitis and Erysipelas: guidance by region

Recommendations, thresholds and pathways can differ. Open the page written for the jurisdiction you need.

United StatesCellulitis and erysipelasInfections · reviewed 2026-08-20CanadaCellulitis and erysipelas (adults)Infections · reviewed 2026-08-20AustraliaCellulitis and erysipelas (adults)Infections · reviewed 2026-08-20

Verified Sources & References

NICE NG141 — Cellulitis and erysipelas
Your learning path

Save your place and choose what comes next

sign in to save your learning

Dermatology · Article 4 of 25