Cellulitis is an acute bacterial infection of the skin.
Cellulitis refers to an acute bacterial skin infection that affects both the dermis and subcutaneous tissue. It may occur anywhere on the body and ranges form a self-limiting infection to severe necrotising infection.
Cellulitis is a very common condition. It can occur at any age, but is mostly seen in middle-aged to older adults and usually affects the lower limbs.
Cellulitis is commonly caused by both Streptococcus and Staphylococcus species.
Cellulitis occurs due to disruption of the skin barrier (e.g. cut, abrasion), which allows entry of microorganisms. Both Streptococcus and Staphylococcus are common skin commensal organisms that can enter the skin and cause infection.
Anything that may affect the integrity of the skin barrier or impair venous/lymph drainage can lead to cellulitis.
Cellulitis is characterised by the hallmarks of inflammation including pain, swelling, warmth and erythema.
Cellulitis is a clinical diagnosis based on the classic appearance of erythematous, warm and oedematous skin.
Laboratory investigations are often unnecessary if the patient is otherwise clinically well. They are more likely to be completed in patients presenting to secondary care (e.g. hospital)
This describes a form of cellulitis that involves the more superficial dermal structures. It is characterised by a raised, well demarcated border and usually occurs secondary to beta-haemolytic streptococcal infection. Treatment is also with antibiotics.
The severity of cellulitis may be assessed using the Eron classification:
Several infective and non-infective aetiologies may be confused with cellulitis.
Often completed as part of the work-up in patients systemically unwell or where an alternative diagnosis is suspected.
If patients are clinically well then further investigations may not be needed. However, if patients are systemically unwell, at risk of deterioration, or suspected of having complications then investigations are warranted.
The principle management of cellulitis is with antibiotics.
Patients with mild cellulitis (e.g. Eron I and some Eron II) may be treated in the community with oral antibiotics. Typical antibiotic choices are penicillin (e.g. phenoxymethylpenicillin) and/or flucloxacillin due to the high rate of streptococcal and staphylococcal infections. Erythromycin/clarithromycin are good alternatives in patients with penicillin allergy (local antibiotics guidelines should always be sought).
Some patients may require hospital admission for assessment and intravenous antibiotics. These include:
Intravenous flucloxacillin, clindamycin and/or vancomycin may be used as intravenous antibiotic choices. Clindamycin is particularly important in patients with suspected group A streptococcal infection as it suppresses bacterial exotoxin production (plus other beneficial effects). Clindamycin may be needed in combination with a beta-lactam antibiotic (e.g. penicillin, cephalosporin, carbapenem).
In patients with severe cellulitis or systemically unwell, advice from microbiology is usually required. It is always recommended to follow local antibiotic guidelines.
Cellulitis may cause life-threatening sepsis or necrotising infections (e.g. necrotising fasciitis).
Have comments about these notes? Leave us feedback