Background Acute lower limb cellulitis is a common yet potentially serious condition. Previous studies have identified risk factors in the non-U.K. population. Ethnicity has been postulated as a possible risk factor but has not previously been investigated. Objectives To identify risk factors for acute lower limb cellulitis in the U.K. population. Methods One hundred and fifty consecutive patients with cellulitis requiring hospital admission and 300 controls were recruited to this prospective case-control study. Controls were matched for age and sex. Results Strongly predictive risk factors for acute lower limb cellulitis in the U.K. include being of white ethnicity and preceding episodes of injury to the affected leg. No systemic illnesses were identified as increasing an individual's risk of presenting with cellulitis. Conclusions This study has identified that patients of white ethnicity are at higher risk of developing acute lower limb cellulitis compared with other ethnic groups. The importance of local risk factors has also been shown in the U.K. population.