Last reviewed: 28 Sep 2021
Last updated: 18 Jun 2021



History and exam

Key diagnostic factors

  • acute onset of red, painful, hot, swollen skin (cellulitis)
  • well-demarcated, bright-red raised skin (erysipelas)

Other diagnostic factors

  • orange-peel appearance
  • blistering
  • bleeding
  • lymphangitis
  • unilaterality
  • fever
  • malaise
  • lymphadenopathy
  • toe-web abnormalities
  • risk factors
  • other constitutional symptoms
  • source of infection
  • immunocompromising factors
  • recent travel
  • fluctuance deep to the cellulitis
  • dermal necrosis
  • signs of sepsis
  • signs of necrotising fasciitis
  • signs of orbital or peri-orbital cellulitis

Risk factors

  • diabetes
  • venous insufficiency
  • eczema
  • oedema and lymphoedema
  • obesity
  • previous episodes of cellulitis
  • toe-web abnormalities

Diagnostic investigations

1st investigations to order

  • full blood count
  • erythrocyte sedimentation rate (ESR)
  • CRP
  • urea and electrolytes
  • blood culture and sensitivities

Investigations to consider

  • skin swab
  • skin aspirate
  • skin biopsy
  • molecular diagnostic procedures
  • plain x-ray
  • MRI
  • ultrasound
  • liver function tests

Treatment algorithm


Expert advisers

Johann Grundlingh, MBChB, FCEM, FFICM, EDICM, DFMS, DipMedTox, MMedTox, MSB, ERT, MEWI, MBA

Emergency Medicine Consultant

Royal London Hospital

Barts Health NHS Trust

Honorary Senior Lecturer

Queen Mary University




JG declares that he has no competing interests.

Ram Narayanan, MBBS, MEM, MRCEM

ST5 in Emergency Medicine

Whipps Cross Hospital

Barts Health NHS Trust




RN declares that he has no competing interests.


BMJ Best Practice would like to gratefully acknowledge the previous expert contributor, whose work has been retained in parts of the content:

Matthew C. Robinson, MD

Infectious Disease Physician

Austin Infectious Disease Consultants



Disclosures: MCR declares that he has no competing interests.

Peer reviewers

Susan Croft, MBChB, MRCP, FRCEM

Emergency Medicine Consultant

Sheffield Teaching Hospitals NHS Foundation Trust




SC declares that she delivered two paid presentations to local general practitioners on acute exacerbations of long-term conditions in March and April 2018 (supported by Astra-Zeneca).


Celia Pincus,

Section Editor, BMJ Best Practice


CP declares that she has no competing interests.

Susan Mayor,

Lead Section Editor, BMJ Best Practice


SM works as a freelance medical journalist and editor, video editorial director and presenter, and communications trainer. In this capacity, she has been paid, and continues to be paid, by a wide range of organisations for providing these skills on a professional basis. These include: NHS organisations, including the National Institute for Health and Care Excellence, NHS Choices, NHS Kidney Care, and others; publishers and medical education companies, including the BMJ Group, the Lancet group, Medscape, and others; professional organisations, including the British Thoracic Oncology Group, the European Society for Medical Oncology, the National Confidential Enquiry into Patient Outcome and Death, and others; charities and patients’ organisations, including the Roy Castle Lung Cancer Foundation and others; pharmaceutical companies, including Bayer, Boehringer Ingelheim, Novartis, and others; and communications agencies, including Publicis, Red Healthcare and others. She has no stock options or shares in any pharmaceutical or healthcare companies; however, she invests in a personal pension, which may invest in these types of companies. She is managing director of Susan Mayor Limited, the company name under which she provides medical writing and communications services.

Tannaz Aliabadi-Oglesby,

Lead Section Editor, BMJ Best Practice


TAO declares that she has no competing interests.

Julie Costello,

Comorbidities Editor, BMJ Best Practice


JC declares that she has no competing interests.

Adam Mitchell,

Drug Editor, BMJ Best Practice


AM declares that he has no competing interests.

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