Association between eye washing and ocular symptoms of hay fever: a mobile app-based prospective cohort study in Japan.

Large-scale analyses of the relationship between eyewash and hay fever symptoms after adjusting for factors associated with allergic symptoms have not yet been conducted. We aimed to evaluate the association between eyewash and ocular symptoms of hay fever. In this digital prospective observational cohort study, we used the AllerSearch smartphone application. Participants reported symptoms (eye itching, tearing, and redness) and their preventive behaviors such as eye washing. Multivariate regression analysis was used to determine the association; temporal changes in ocular symptoms were compared using a mixed-effects model. Of 476 included participants, 71 practiced eye washing. Eyewash group had milder symptoms than non-eyewash group (estimated difference between the two groups, 95% confidence interval): eye itching (- 0.851 points, - 1.369 to - 0.333, P = 0.001), tearing (- 0.655 points, - 1.217 to - 0.094, P = 0.022), total ocular symptoms score (- 0.840 points, - 1.481 to - 0.198, P = 0.010), and total Japanese Allergic Conjunctival Disease Quality of Life Questionnaire score (- 5.983 points, - 9.633 to - 2.333, P = 0.001). Longitudinal analysis indicated that eyewash group maintained milder ocular symptoms over time, with more symptom-free days. In conclusion, eye washing was associated with milder ocular symptoms of hay fever.