Cellulitis and Erysipelas

NICE guideline [NG141] Cellulitis and erysipelas: antimicrobial prescribing. Published: Sep 2019.

NICE CKS Cellulitis – acute. Last revised: Oct 2025.

Article Last Updated:26/05/2026

Cellulitis and Erysipelas

Cellulitis and erysipelas are acute bacterial skin infections. Cellulitis is a deep skin infection affecting the dermis and subcutaneous tissues, while erysipelas is a more superficial form of cellulitis affecting the upper dermis. They are managed using similar antimicrobial principles.

This updated UKMLA guide to cellulitis and erysipelas is based on NICE NG141 and NICE CKS, which covers causes, risk factors, symptoms, complications, diagnosis, and management.

Causes

Cellulitis vs erysipelas:

Cellulitis: deep skin infection, involving the dermis and subcutaneous tissue
Erysipelas: superficial skin infection, involving only the upper dermis

Cellulitis develops when microorganisms enter the dermal and subcutaneous tissues via disruptions in the skin barrier.

The most common infective organisms for cellulitis and erysipelas in adults:

Group A Streptococcus (Streptococcus pyogenes) – most common ^[Ref]
Staphylococcus aureus

Some textbooks and traditional teaching state that erysipelas is primarily caused by Group A Streptococcus (Streptococcus pyogenes).

Some less common organisms, but classically associated with certain exposures:

Contaminated hot tubs, sponges, or a nail puncture wound → Pseudomonas aeruginosa
Aquarium keepers → Mycobacterium marinum
Following cat or dog bites → Pasteurella multocida and Capnocytophaga canimorsus
Following a human bite or fist injuries → Eikenella corrodens
Following a rat bite → Streptobacillus moniliformis

Risk Factors

Most cases arise from bacterial infection through a skin break, such as:

Trauma (e.g. bite, laceration, burn)
Ulcers (esp. lower limb ulcers)
Surgery
Concomitant skin disorder (e.g. atopic eczema)

Other risk factors:

Diabetes and other causes of immunosuppression
Lymphoedema / oedema (e.g. lower limb oedema in CKD or heart failure)
Venous insufficiency
Obesity
Pregnancy
Previous cellulitis (recurrence is common)

Clinical Features

Typical presenting features of cellulitis:

Location

More common in the lower limbs

Classically unilateral (bilateral cellulitis is rare)

Appearance

Acute onset of:

Red, hot, swollen, tender skin
The redness and affected skin area spread rapidly
Lesion with diffuse / ill-defined borders

Systemic signs

Fever
Malaise
Other symptoms, such as rigours and nausea may be present but are uncommon

Erysipelas can be clinically distinguished from cellulitis by its raised, well-demarcated borders (as opposed to the diffuse / ill-defined borders in cellulitis)

The face is a common site of erysipelas.

Complications

Key acute complications:

The infection may spread to deeper tissue, causing
- Necrotising fasciitis (involving the deep subcutaneous tissues and fascia)
- Myositis (involving the muscles)
Sepsis
Subcutaneous abscesses

Investigation and Diagnosis

Cellulitis and erysipelas are primarily clinical diagnoses based on clinical features (see above).

Consider drawing around the borders (edge of the redness) with a surgical marker pen to monitor progress, before treatment.

Only consider taking a swab for microbiology to guide treatment if:

Skin is broken, and
Penetrating injury / exposure to water-borne organisms / infection acquired outside the UK

Severity Classification

The Eron classification system is used to stratify cellulitis severity:

Eron Class	Description
I	No systemic toxicity, and No uncontrolled comorbidities
II	Systemically unwell, or With comorbidity (e.g. diabetes, PAD, chronic venous insufficiency, morbid obesity)
III	Significant systemic upset (e.g. acute confusion, tachycardia, tachypnoea, hypotension), or Vascular compromise, or Unstable comorbidities
IV	Sepsis, or Life-threatening infection (e.g. necrotising fasciitis)

Management

Both cellulitis and erysipelas share essentially the same management principles. NICE has produced a single antimicrobial guideline covering both conditions.

Admission Criteria

Refer the following patients to hospital:

Eron class II-IV (see above)
Severely immunocompromised patients
Other serious conditions
- Septic arthritis
- Osteomyelitis
- Orbital cellulitis (consider admission for periorbital/preseptal cellulitis)

Referral urgency should be based on clinical judgement. For instance, it is sensible to refer immediately to the emergency department in Eron class IV.

Antibiotic Therapy

Consider drawing around the borders (edge of the redness) with a surgical marker pen to monitor progress, before treatment.

Oral antibiotics are typically 1st line, unless the patient cannot tolerate oral medications / severely unwell → IV antibiotics.

Choice of antibiotics:

Scenario / patient population	Recommended antibiotics
Standard choice (most patients)	1st line: flucloxacillin (5-7 days) 2nd line (e.g. penicillin allergic): clarithromycin / erythromycin / doxycycline (avoid in children)
Pregnant women	1st line: flucloxacillin (penicillin is safe during pregnancy) 2nd line: erythromycin
Infection near the eyes or nose (including periorbital / preseptal cellulitis)	1st line: co-amoxiclav 2nd line (e.g. penicillin allergic): clarithromycin + metronidazole
Severe infection (including orbital cellulitis)	ANY of the following: Co-amoxiclav Cefuroxime Clindamycin Ceftriaxone (only IV route available)
Suspected / confirmed MRSA infection	Dual therapy of: Flucloxacillin, PLUS Vancomycin OR teicoplanin OR linezolid