The study design ensured assessment of eligibility before and after the study product was provided to the participants. A summary of the study design and an overview of the schedule of activities can be found in Figure 1 and Supplemental Table 1, respectively. The first two steps of the study protocol were the pre-screening stage, and the screening stage. At the pre-screening stage, eligible participants were invited via email to download the study app and participants completed an eIC. Participants had an interview phone call with a medically qualified investigator to confirm personal details and medical history (Figure 1 and Supplemental Methods Sections 1 and 2). At the screening stage, participants who provided the eIC were asked to complete the Wisconsin Upper Respiratory Symptom Survey-21 (WURSS-21) 17 and the additional QoL questions as baseline assessments. Participants also confirmed their medical history, concomitant medication, and completed a product shipping form (Figure 1 and Supplemental Methods Sections 3–5). Participants completed the baseline questionnaires from the 7 November 2022; the last questionnaire was completed on the 20 December 2022.