Reviewed and revised 24 May 2014


Cellulitis is an uncomplicated non-necrotizing acute infection of the skin involving the hypodermis (mid-to-lower dermis and subcutaneous tissue) and spares deeper structures such as fascia and muscle.


Typical organisms

  • Streptococcus pyogenes
  • Staphylococcus aureus

These risk factors confer a predisposition for cellulitis:

  • Diabetes mellitus.
  • Vascular insufficiency
  • Peripheral vascular disease
  • Chronic venous insufficiency
  • Chronic lymphoedema
  • loss of skin integrity, due to:
    • Penetrating trauma (including retained foreign bodies)
    • Insect or animal bites
    • Chronic inflammatory dermatoses (such as psoriasis or eczema)
    • Chronic skin infections (e.g. Tinea)
  • Radiotherapy


Cellulitis typically has these features

  • Acute onset
  • Painful erythematous area of inflamed skin (not elevated, ill defined demarcation boundary)
  • tender and warm on palpation
  • most common on the lower limbs
  • rarely bilateral

If more severe

  • Lymphangitis
  • Lymphadenopathy
  • Systemic features: fever and constitutional symptoms (e.g. headache, malaise, lethargy, anorexia)

Follows usual natural history

  •  progression of erythema +/- fever  up to 72 hours after starting appropriate antibiotics
  •  erythema gradually resolves over weeks, discolouration persists for months in some cases

Risk factors may be present


  • Erysipelas
    • a superficial variant of cellulitis involving only the upper dermis and superficial cutaneous lymphatics.
    • characterised by a well demarcated area of erythema raised above the level of the surrounding skin
  • Deeper infections
    • these are far more serious and may involve fascia (e.g. necrotizing fasciitis) or muscle (e.g. pyomyositis, clostridial myonecrosis/ gangrene)
    • severe pain, systemically unwell, +/- subcutaneous crepitus, rapidly progressive
  • Lipodermatosclerosis
    • chronic erythema and pain with episodic exacerbation in patients with venous insufficiency
    • typically bilateral, lacks systemic features and not warm to touch
  • stasis dermatitis
  • contact dermatitis
  • lymphoedema
  • eosinophilic cellulitis (Well’s syndrome)
  • papular urticaria
  • fixed drug reactions
  • burns


  • Usually only needed systemically unwell, severe or uncertain  of diagnosis

Laboratory tests

  •  FBE, CRP, UEC, glucose


  • XR to exclude foreign body
  • U/S to exclude foreign body, rule out abscess; may show marbling appearance of cellulitis, diagnose soft tissue gas forming infections
  • CT/MRI if need to exclude fasciitis or myonecrosis (must not delay operative therapy if indicated)



  • if indicated

Specific antibiotic therapy (Adjust does in renal/ hepatic dysfunction)

  • oral antibiotics for uncomplicated cellulitis
    • Flucloxacillin 1g q6h for 7-10d or cephalexin 1g q6h for 7-10d
    • If immediate penicillin hypersensitivity:  Clindamycin 450 mg orally 8 hourly, (7-10 days)
  • IV Antibiotics for failure of oral antibiotics or complicated cases
    • Flucloxacillin 1-2g IV q6h or Cephazolin 1-2g IV q8h
    • If immediate penicillin hypersensitivity: Clindamycin 450 mg IV q8h or  Vancomycin 1.5g IV q12h

Supportive care and monitoring

  • Resting and elevating (where possible) the effected part; can consider the use of a POP backslab
  • Analgesia (oral may be sufficient)


Admission to hospital is generally warranted if:

  • significant co-morbidities (especially if immunosuppressed)
  • unable to tolerate oral medication
  • social issues that impact care and GP follow up
  • complications (e.g. systemically unwell, trauma/ need for debridement, deep soft tissue infections)
  • special sites (periorbital, perineal)

The appropriate admitting team may vary between hospitals

  • observation ward
  • hospital in the home
  • general medicine
  • general surgery

Surgical consult if:

  • suspected deep soft tissue infection
  • face or hands (usually Plastics)
  • periorbital or orbital cellulitis (Ophthalmology)
  • peritonsillar cellulitis (ENT)

References and links

Journal articles

  • Adhikari S, Blaivas M. Sonography first for subcutaneous abscess and cellulitis evaluation. J Ultrasound Med. 2012 Oct;31(10):1509-12. PubMed PMID: 23011612.
  • Keller EC, Tomecki KJ, Alraies MC. Distinguishing cellulitis from its mimics. Cleve Clin J Med. 2012 Aug;79(8):547-52. doi: 10.3949/ccjm.79a.11121. PubMed PMID: 22854433.
  • Phoenix G, Das S, Joshi M. Diagnosis and management of cellulitis. BMJ. 2012 Aug 7;345:e4955. PMID: 22872711.

CCC 700 6

Critical Care


Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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