BACKGROUND: Patient-reported outcome measures (PROMs) are commonly used in eczema clinical trials. Several trials have used PROMs weekly for symptom monitoring. However, the increased frequency of patient-reported symptom monitoring may prompt participants to enhance the self-management of eczema and increase standard topical treatment use that can lead to improvements in outcomes over time. This is concerning as weekly symptom monitoring may constitute an unplanned intervention, which may mask small treatment effects and make it difficult to identify changes in the eczema resulting from the treatment under investigation. OBJECTIVES: To evaluate the effect of weekly patient-reported symptom monitoring on participants' outcomes and to inform the design of future eczema trials. METHODS: This was an online parallel-group nonblinded randomized controlled trial. Parents/carers of children with eczema and young people and adults with eczema were recruited online, excluding people scoring < 3 points on the Patient Oriented Eczema Measure (POEM), to avoid floor effects. Electronic PROMs were used for data collection. Participants were allocated using online randomization (1 : 1) to weekly POEM for 7 weeks (intervention) or no POEM during this period (control). The primary outcome was change in eczema severity based on POEM scores, assessed at baseline and week 8. Secondary outcomes included change in standard topical treatment use and data completeness at follow-up. Analyses were conducted according to randomized groups in those with complete data at week 8. RESULTS: A total of 296 participants were randomized from 14 September 2021 to 16 January 2022 (71% female, 77% white, mean age 26.7 years). The follow-up completion rate was 81.7% [n = 242; intervention group, n = 118/147 (80.3%); control group n = 124/149 (83.2%)]. After adjusting for baseline disease severity and age, eczema severity improved in the intervention group (mean difference in POEM score -1.64, 95% confidence interval -2.91 to -0.38; P = 0.01). No between-group differences were noted in the use of standard topical treatments and data completeness at follow-up. CONCLUSIONS: Weekly patient-reported symptom monitoring led to a small perceived improvement in eczema severity.