Cellulitis

Cellulitis is a bacterial infection that affects the dermis and the deeper subcutaneous tissues. It is one of the most common conditions seen in the acute medical setting and is usually diagnosed clinically. Cellulitis is most commonly caused by infection with Streptococcus pyogenes or less commonly Staphylcoccus aureus. The majority of cases resolve with oral antibiotics.

Features

commonly occurs on the shins
- usually unilateral - bilateral cellulitis is rare and suggests an alterative diagnosis
erythema
- generally reasonably well-defined margins but some cases may present with diffuse erythema
- blisters and bullae may be seen with more severe disease
swelling
systemic upset
- fever
- malaise
- nausea

Cellulitis of the right lower leg. Note the diffuse erythema and swelling.

The diagnosis of cellulitis is clinical. No further investigations are required in primary care. Bloods and blood cultures may be requested if the patient is admitted and septicaemia is suspected.

Criteria for admission

The Eron classification system can be used to guide how we manage patients with cellulitis: #link1

Class	Features
I	There are no signs of systemic toxicity and the person has no uncontrolled co-morbidities
II	The person is either systemically unwell or systemically well but with a co-morbidity (for example peripheral arterial disease, chronic venous insufficiency, or morbid obesity) which may complicate or delay resolution of infection
III	The person has significant systemic upset such as acute confusion, tachycardia, tachypnoea, hypotension, or unstable co-morbidities that may interfere with a response to treatment, or a limb-threatening infection due to vascular compromize
IV	The person has sepsis syndrome or a severe life-threatening infection such as necrotizing fasciitis

They recommend the following that we admit for intravenous antibiotics the following patients: #link2

Has Eron Class III or Class IV cellulitis.
Has severe or rapidly deteriorating cellulitis (for example extensive areas of skin).
Is very young (under 1 year of age) or frail.
Is immunocompromized.
Has significant lymphoedema.
Has facial cellulitis (unless very mild) or periorbital cellulitis.

The following is recommended regarding Eron Class II cellulitis:

Admission may not be necessary if the facilities and expertise are available in the community to give intravenous antibiotics and monitor the person - check local guidelines.

Other patients can be treated with oral antibiotics.

Management

Management is guided by the Eron classification.

Eron Class I

oral antibiotics NICE
oral flucloxacillin as first-line treatment for mild/moderate cellulitis
oral clarithromycin, erythromycin (in pregnancy) or doxycycline is recommended in patients allergic to penicillin

Eron Class II

NICE recommend: 'Admission may not be necessary if the facilities and expertise are available in the community to give intravenous antibiotics and monitor the person - check local guidelines.'

Eron Class III-IV

admit
NICE recommend: oral/IV co-amoxiclav, oral/IV clindamycin, IV cefuroxime or IV ceftriaxone

+PassMedicine Notes

Cellulitis is a bacterial infection that affects the dermis and the deeper subcutaneous tissues. It is one of the most common conditions seen in the acute medical setting and is usually diagnosed clinically. Cellulitis is most commonly caused by infection with Streptococcus pyogenes or less commonly Staphylcoccus aureus. The majority of cases resolve with oral antibiotics.

Features

commonly occurs on the shins

usually unilateral - bilateral cellulitis is rare and suggests an alterative diagnosis

erythema

generally reasonably well-defined margins but some cases may present with diffuse erythema
blisters and bullae may be seen with more severe disease

swelling
systemic upset

fever
malaise
nausea

The diagnosis of cellulitis is clinical. No further investigations are required in primary care. Bloods and blood cultures may be requested if the patient is admitted and septicaemia is suspected.

Criteria for admission

The Eron classification system can be used to guide how we manage patients with cellulitis: #link1

Class _ Features| I _ There are no signs of systemic toxicity and the person has no uncontrolled co-morbidities| II _The person is either systemically unwell or systemically well but with a co-morbidity (for example peripheral arterial disease, chronic venous insufficiency, or morbid obesity) which may complicate or delay resolution of infection| III _ The person has significant systemic upset such as acute confusion, tachycardia, tachypnoea, hypotension, or unstable co-morbidities that may interfere with a response to treatment, or a limb-threatening infection due to vascular compromize| IV _ The person has sepsis syndrome or a severe life-threatening infection such as necrotizing fasciitis| They recommend the following that we admit for intravenous antibiotics the following patients: #link2

Has Eron Class III or Class IV cellulitis.
Has severe or rapidly deteriorating cellulitis (for example extensive areas of skin).
Is very young (under 1 year of age) or frail.
Is immunocompromized.
Has significant lymphoedema.
Has facial cellulitis (unless very mild) or periorbital cellulitis.

The following is recommended regarding Eron Class II cellulitis:

Admission may not be necessary if the facilities and expertise are available in the community to give intravenous antibiotics and monitor the person - check local guidelines.

Other patients can be treated with oral antibiotics.

Management

Management is guided by the Eron classification.

Eron Class I

oral antibiotics NICE
oral flucloxacillin as first-line treatment for mild/moderate cellulitis
oral clarithromycin, erythromycin (in pregnancy) or doxycycline is recommended in patients allergic to penicillin

Eron Class II

NICE recommend: 'Admission may not be necessary if the facilities and expertise are available in the community to give intravenous antibiotics and monitor the person - check local guidelines.'

Eron Class III-IV