Abstract Background Emollients and topical corticosteroids (TCS) prevent and treat flares in eczema. However, topical treatment use is poorly recorded and reported in clinical trials. There is no clear consensus of how best to capture and summarize topical treatment use. Objectives To explore different ways of capturing and reporting topical treatment use in childhood eczema. Methods This was a secondary data analysis using 450 participants from the Best Emollients for Eczema (BEE) trial. Participants were allocated to use one type of emollient (lotion, cream, gel or ointment) ‘twice daily and when required’ for 16 weeks. Otherwise, clinical management remained unchanged. Parents completed weekly questions about topical therapy use and eczema symptoms. Two versions of topical treatment use questionnaires were used. The first (n = 202, 44.9%) asked parents to report treatment use on days 1–7, starting completion on the day they were randomized. The second (n = 248, 55.1%) reported use by day of the week (Monday to Sunday), starting completion the first Monday after randomization. Both underwent patient and public involvement review but the second version was tested more thoroughly using cognitive interviewing techniques, following parent feedback that questions on the first version were confusing. Descriptive statistics compared questionnaire completion and differences in emollient and TCS use. Results Overall, questionnaire completion for both emollient and TCS use decreased with time, but at weeks 1 and 16, it was 84.7% (381/450) and 58.9% (265/450) for emollient use, and 94.2% (424/450) and 80.4% (362/450) for TCS use, respectively. Fewer emollient use questionnaires were completed with the first (33.5%, 1082/3232 patient-weeks) than the second (87.9%, 3489/3968 patient-weeks) version (P < 0.001). TCS use questionnaire completion were similar for both (84.9%, 2744/3232 patient-weeks and 87.4%, 3468/3968 patient-weeks, P = 0.002). We present different ways of summarizing topical treatment use. Conclusions Although questionnaire completion was similar for TCS use, emollient-use data completeness was higher in the second version. When designing questionnaires, balancing the detail and complexity of questions is important, especially if being collected as a secondary outcome measure. Numerous ways of summarizing the same data can provide different information. Future collection and reporting of treatment use should reflect specific trial aims.