A Clinical Prediction rule (CPR) is a decision-making tool that comes from original research as opposed to the opinion of experts. We intend to create a preliminary CPR to decide which patients require oral and which patients require intravenous antibiotics for cellulitis from their first visit to an emergency department. The aim of this is to provide safer care by reducing the risk of a patient returning to the hospital with a worsening infection. It will also promote more cost-effective care by reducing hospital re-attendance rates and wasted antibiotics.