• Cellulitis presents with an acute onset of red, painful, hot, swollen, and tender skin, with possible blister or bullae formation.
• Fever, malaise, nausea, shivering and rigors may accompany or precede the skin changes. Later, in more severe cases, there may be spreading lymphangitis of the same limb.
• Cellulitis usually affects one limb only (depending on the cause).
• Rule out other diagnoses (see Differential diagnosis).

These recommendations are based on Guidelines on the management of cellulitis, published by the Clinical Resource Efficiency Support Team [CREST, 2005].

• On the legs, conditions that commonly mimic cellulitis include:
• Varicose eczema (but this is usually bilateral with crusting, scaling, and itch).
• Deep venous thrombosis (but this does not usually cause significant erythema; see the CKS topic on Deep vein thrombosis).
• Other less common conditions which may initially present with similar signs and symptoms to cellulitis include:
• Necrotizing fasciitis.
• Gangrene.
• Acute gout.
• Adverse drug reactions.
• Metastatic cancer (carcinoma erysipeloides).

These recommendations are based on Guidelines on the management of cellulitis, published by the Clinical Resource Efficiency Support Team [CREST, 2005].

• Consider taking a swab if there is a visible portal of entry for bacteria (e.g. an open wound); other investigations are not usually necessary.

This recommendation is based on Guidelines on the management of cellulitis, published by the Clinical Resource Efficiency Support Team [CREST, 2005].

• Culture taken from a swab of broken skin (before antibiotic treatment is started) may be useful if empirical treatment proves to be ineffective; however, yields from such swabs tend to be low [Bishara et al, 2001; Swartz and Pasternack, 2005]. Other investigations (e.g. blood tests) are only required if the person is ill enough to warrant admission to hospital.