In a patient presenting with recurrent cellulitis (defined as two or more episodes in the previous 12 months), investigations should focus on identifying and excluding underlying conditions that predispose to recurrence. These include assessing for oedema, diabetes mellitus, venous insufficiency, lymphoedema, eczema, leg ulcers, and tinea pedis. Clinical evaluation should include examination for these conditions and relevant investigations such as blood glucose testing to exclude diabetes, and assessment of venous function if venous insufficiency is suspected. Referral to specialist clinics (e.g., lymphoedema clinics) may be appropriate for further assessment. Additionally, consider microbiological investigations if infection is not responding to treatment or if unusual pathogens are suspected. Imaging or specialist referral may be warranted if complications or alternative diagnoses (such as osteomyelitis or necrotising fasciitis) are suspected. Routine investigations to exclude other underlying causes should be guided by clinical findings and specialist advice.
Specifically, NICE guidelines recommend considering underlying conditions such as oedema, diabetes, and venous insufficiency when deciding on prophylactic antibiotic use and management of recurrent cellulitis. Referral to secondary care for advice on prophylaxis is advised after at least two episodes within 12 months, taking into account underlying conditions and their management NICE CKS.