What clinical features should I assess to differentiate cellulitis from other skin infections?

Clinical features to assess to differentiate cellulitis from other skin infections include:

• Presence of spreading redness and swelling beyond the initial lesion, noting that some initial spreading may occur and redness may be less visible on darker skin tones.
• Severe pain that is out of proportion to the visible infection.
• Signs of systemic illness such as fever, tachycardia, tachypnoea, hypotension, or confusion.
• Local signs such as warmth, tenderness, and swelling of the affected area.
• Presence of lymphangitis (red streaking) or regional lymphadenopathy.
• Exclusion of other conditions by assessing for features suggestive of necrotizing fasciitis (severe pain, rapid progression), erysipelas (sharply demarcated raised edges), abscess formation (fluctuant swelling), or other skin infections like fungal infections or diabetic foot infections.
• Consideration of risk factors such as lymphoedema, venous insufficiency, diabetes, eczema, or leg ulcers that predispose to cellulitis.
• Monitoring progression by marking the edge of the erythema with a surgical marker pen to distinguish spreading cellulitis from other rashes.

These features help differentiate cellulitis, which typically presents as an acute spreading bacterial infection of the skin and subcutaneous tissues, from other skin infections that may have different clinical presentations and management pathways.

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