Introduction: Despite several expert panel recommendations and cellulitis treatment guidelines, there are currently no clinical decision rules to assist clinicians in deciding which emergency department (ED) patients should be treated with oral antibiotics and which patients require intravenous therapy at first presentation of uncomplicated cellulitis. The objective of this prospective study is to determine potential patient risk factors associated with adult patients (>17years) presenting to the ED with a concern about a skin or soft tissue infection who fail initial antibiotic therapy for the treatment of standard cellulitis and require a change of antibiotics or admission to hospital.