ObjectiveTo assess the effectiveness of a potent topical corticosteroid (TCS) as an initial treatment in primary care for children with moderate flare-ups of atopic dermatitis (AD), compared to starting on a mild TCS.DesignAn observational prospective cohort study with an embedded pragmatic multicentre open-label randomised controlled trial.SettingA total of 53 general practices in the southwest of the Netherlands took part in the study.Participants209 children aged 3 months to 17 years diagnosed with AD (International Classification of Primary Care codes S87 or S88) who visited their general practitioner (GP) for AD or received repeat prescriptions for AD in the previous 12 months were included in the cohort study through the general practices. Finally, 32 patients (15%) were randomised and assigned to the trial (13 girls; 19 boys; median age 4.0 years).InterventionsIf cohort participants experienced a moderate flare-up (ie, need to intensify topical treatment from the child’s and/or parents’ point of view of AD and a three-item severity score from three to<6 scored by their GP) during cohort follow-up, they were randomised to either the intervention group, a strong TCS (class III, fluticasone propionate 0.05%), or the control group, a mild TCS (class I, hydrocortisone acetate 1%).Primary and secondary outcome measuresWe measured outcomes at baseline and at 1, 4 and 24 weeks. The primary outcome was AD-related symptoms (Patient-Oriented Eczema Measure (POEM) score) measured over 24 weeks of follow-up. Secondary outcomes included the Eczema Area and Severity Index, the Investigators Global Assessment, quality of life (QoL), Patient Global Assessment, Numeric Itch Intensity Score and TCS use.ResultsThe primary outcome showed a significant difference in the POEM scores over 24 weeks of follow-up between the intervention group (n=17) and the control group (n=15) (3.3 vs 9.4, p=0.023). The potent TCS also significantly improved the POEM at 1 week (5.5 vs 12.0, p=0.042) and 4 weeks (4.3 vs 12.7, p=0.030). Improvement in the QoL was significant at 4 weeks (1.0 vs 4.5, p=0.014) and 24 weeks (0.0 vs 2.0, p=<0.000).ConclusionDespite the small sample size, the data suggests a clinical benefit from starting with a potent TCS rather than a mild TCS when a flare-up of AD is moderate.Trial registrationThe Netherlands National Trial Register: NTR6679.