Abstract Background Questions about washing are a high priority for people with eczema (syn. atopic dermatitis, atopic eczema) but are rarely the focus of randomised controlled trials (RCTs). Objectives To assess the impact of weekly bathing compared to daily bathing in people with eczema in the first of a series of eczema citizen science online trials in the United Kingdom. Methods Pragmatic, two-arm, parallel-group superiority RCT. People with self-reported eczema aged ≥1 were eligible, excluding those with very mild eczema (Patient Orientated Eczema Measure (POEM) score ≤ 2). Participants were allocated (1:1) using minimisation, balancing on eczema severity (POEM), age and usual method of bathing, to either the weekly bathing group (bath or shower once or twice a week) or the daily bathing group (≥6 times a week) for 4 weeks. Participants were not blinded to their allocation. Primary outcome was participant reported eczema symptoms collected weekly over four weeks using POEM (range 0 to 28, higher scores more severe). Results 438 people with eczema (108 aged <16 years) were randomised between 29th January and 8th July 2024: 218 to daily bathing and 220 to weekly bathing. The primary analysis included 195 participants (89%) allocated to daily bathing and 193 (88%) to weekly bathing who completed at least one follow-up questionnaire. Mean POEM scores at baseline, 1, 2, 3 and 4 weeks, were 14.5 [standard deviation 5.7], 11.7 [5.9], 12.2 [5.9], 11.7 [6.7] and 11.6 [6.5], respectively, in the daily bathing group, and 14.9 [6.3], 12.1 [6.8], 11.3 [6.7], 10.5 [7.0] and 10.6 [7.2] in the weekly bathing group. The adjusted difference in mean POEM score over 4 weeks for weekly versus daily bathing was -0.4 (95% confidence interval -1.3 to 0.4, p = 0.30). Process evaluation data highlighted participants’ experiences of making changes to bathing routines, including barriers to following the allocated routine. No serious unintended effects or harms were reported. Conclusions The trial found no evidence of a difference in eczema symptoms between bathing or showering weekly compared to daily. These results are helpful for people with eczema, giving them the freedom to choose what suits them best.