Investigations

Erysipelas is diagnosed in most cases from history and examination (1)

Do not take blood for culture routinely, but only if the patient needs admission (2). This may be indicated by systemic symptoms and signs, such as hypotension, tachycardia, or pyrexia and immunocompromising factors.

In patients who are systemically ill and/or have comorbidities, send blood for (3):

• FBC
• ESR or CRP (there is often a raised CRP level but a normal CRP level does not rule out infection) (4)
• Urea and electrolytes

Treatment should not be delayed awaiting results.

Reference:

1. Edwards G, Freeman K, Llewelyn MJ, et al. What diagnostic strategies can help differentiate cellulitis from other causes of red legs in primary care? BMJ. 2020 Feb 12;368:m54.
2. Sullivan T, de Barra E. Diagnosis and management of cellulitis. Clin Med (Lond). 2018 Mar;18(2):160-3.
3. Clinical Resource Efficiency Support Team. Guidelines on the management of cellulitis in adults. June 2005 [internet publication].
4. Phoenix G, Das S, Joshi M. Diagnosis and management of cellulitis. BMJ. 2012 Aug 7;345:e4955.