Ciclosporin is used to treat severe atopic dermatitis (AD) where conventional therapy is either ineffective or inappropriate. Response to treatment is variable and the factors determining responsiveness are currently unclear. The aim of this study was to determine which children with severe AD are most responsive. A cohort of 35 children with severe AD who were given oral ciclosporin was retrospectively surveyed. SCORAD index was used to assess severity prior to and after treatment. Demographic and clinical data were correlated with clinical response. Ciclosporin resulted in a sustained reduction in SCORAD index of 91 (67-100)% in children where clinical skin infection was the main trigger and in whom the infection was effectively eradicated with antibiotics. If infection persisted or recurred the reduction in SCORAD index was only 44 (41-83)%. Children in whom their AD was triggered by other factors had a poor response to ciclosporin with reduction in SCORAD index of 8 (1-39)%. Oral ciclosporin is most effective in children with infection-driven AD in whom the infection is brought under control. In cases where the infection recurs or where the main triggers are non-infectious, response to ciclosporin is poorer.