Cellulitis and erysipelas

Last reviewed: 7 May 2023

Last updated: 26 Jan 2023

Cellulitis is an infection of the deep dermis and subcutaneous tissue; erysipelas is more superficial, involving only the upper dermis and superficial lymphatics.

The most common causative bacteria are Streptococcus pyogenes and Staphylococcus aureus, but infection can be caused by Streptococcus pneumoniae, Haemophilus influenzae, gram-negative bacilli, and anaerobes.

Usually make the diagnosis based on history and examination only, although consider swab and aspiration cultures if cellulitis is associated with a break in the skin. Take blood for culture in patients who require admission.

Prior episodes of cellulitis, pre-existing lymphoedema or venous insufficiency, diabetes, obesity, and tinea pedis can all predispose to this condition.

Target antibiotics at the most common causes (streptococci and S aureus) and treat predisposing conditions.

Definition

Cellulitis is an acute spreading infection of the skin with visually indistinct borders that principally involves the dermis and subcutaneous tissue. It is characterised by redness, swelling, heat, and tenderness, and commonly occurs in an extremity.

Erysipelas is a distinct form of superficial cellulitis with notable lymphatic involvement. It is raised and sharply demarcated from uninvolved skin.

Animal bites (including human bites), surgical wound infections, diabetic foot infections, and cellulitis or erysipelas in children and pregnant women are beyond the scope of this topic. See our topics Animal bites and Diabetic foot infections.

History and exam

Key diagnostic factors

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

Full details

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

Full details

Risk factors

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

Full details

Diagnostic investigations

1st investigations to order

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

Full details

Investigations to consider

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

Full details

Treatment algorithm

INITIAL

suspected sepsis

ACUTE

severe: any site (excluding near the eyes or nose)

any severity: site near eyes or nose

non-severe: any site (excluding near eyes or nose)

ONGOING

frequent relapses

Contributors

Expert advisers

Alexander Alexiou, MBBS, BSc, DCH, FRCEM, Dip IMC RCSEd

Emergency Medicine Consultant

Barts Health NHS Trust

Physician Response Unit Consultant

London’s Air Ambulance

Royal London Hospital

Disclosures

AA declares that he has no competing interests.

Ram Narayanan, MBBS, MEM, MRCEM

ST5 in Emergency Medicine

Whipps Cross Hospital

Barts Health NHS Trust

London

Disclosures

RN declares that he has no competing interests.

Acknowledgements

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

Matthew C. Robinson, MD

Infectious Disease Physician

Austin Infectious Disease Consultants

Austin

Disclosures: MCR declares that he has no competing interests.

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

London

Disclosures: JG declares that he has no competing interests.

Peer reviewers

Susan Croft, MBChB, MRCP, FRCEM

Emergency Medicine Consultant

Sheffield Teaching Hospitals NHS Foundation Trust

Sheffield

Disclosures

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).

Editors

Celia Pincus

Section Editor, BMJ Best Practice

Disclosures

CP declares that she has no competing interests.

Susan Mayor

Lead Section Editor, BMJ Best Practice

Disclosures

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

Disclosures

TAO declares that she has no competing interests.

Julie Costello

Comorbidities Editor, BMJ Best Practice

Disclosures

JC declares that she has no competing interests.

Adam Mitchell

Drug Editor, BMJ Best Practice

Disclosures

AM declares that he has no competing interests.

Differentials
- Necrotising fasciitis
- Thrombophlebitis, superficial
- Deep vein thrombosis
More Differentials
Guidelines
- Appropriate use of short-course antibiotics in common infections: best practice advice from the American College of Physicians
- Cellulitis and erysipelas: antimicrobial prescribing
More Guidelines
Patient leaflets
Cellulitis and erysipelas
More Patient leaflets
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Cellulitis and erysipelas

Summary

Definition

History and exam

Key diagnostic factors

Other diagnostic factors

Risk factors

Diagnostic investigations

1st investigations to order

Investigations to consider

Treatment algorithm

suspected sepsis

severe: any site (excluding near the eyes or nose)

any severity: site near eyes or nose

non-severe: any site (excluding near eyes or nose)

frequent relapses

Contributors

Expert advisers

Alexander Alexiou, MBBS, BSc, DCH, FRCEM, Dip IMC RCSEd

Disclosures

Ram Narayanan, MBBS, MEM, MRCEM

Disclosures

Acknowledgements

Peer reviewers

Susan Croft, MBChB, MRCP, FRCEM

Disclosures

Editors

Celia Pincus

Disclosures

Susan Mayor

Disclosures

Tannaz Aliabadi-Oglesby

Disclosures

Julie Costello

Disclosures

Adam Mitchell

Disclosures

Differentials

Guidelines

Patient leaflets

Log in or subscribe to access all of BMJ Best Practice

Log in or subscribe to access all of BMJ Best Practice

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