What diagnostic strategies can help differentiate cellulitis from other causes of red legs in primary care?

### What you need to know Cellulitis is the most common bacterial infection causing red legs. It is treated with antibiotics, and patients with severe disease may need to be hospitalised.1234 In 2017-18, 317 522 patients were given a diagnosis of cellulitis in UK hospitals.5 The true incidence, including patients managed through primary care, is likely to be higher. Redness is often accompanied by other classic signs of inflammation: tenderness, warmth, and swelling. Other causes of red legs can present with some, or all, of these common symptoms6 (table 1). These conditions may be misdiagnosed as cellulitis. Studies in US emergency departments have reported that between 28% and 30.7%789 of cellulitis diagnoses are incorrect. Misdiagnosis can result in unnecessary antibiotic treatment10 and hospitalisation. Conversely, untreated cellulitis can have complications such as extensive tissue damage and necrosis, disseminated infection, septic shock, and potentially death.11Figures 1 and 2 show alternative diagnoses for red legs. View this table: Table 1 Distinguishing cellulitis from other causes of red legs. Major alternatives to consider and diagnostic considerations, adapted from clinical guidelines124 Fig 1 Alternative diagnoses of red legs: (a) cellulitis, (b) varicose eczema, (c) deep vein thrombosis, (d) gout Fig 2 Concurrent cellulitis and deep vein thrombosis. The manifestation of skin diseases can vary between ethnic groups and skin colours Differentiating red legs …