The Association Between Repeated Lip Augmentation With Hyaluronic Acid Filler and Recurrence of Herpes Labialis: A Longitudinal Self-controlled Study.

Background: Recurrent herpes labialis (RHL) is a common condition characterized by episodic viral reactivation triggered by local or systemic factors. Hyaluronic acid (HA) lip augmentation is widely performed for aesthetic purposes, yet its potential association with changes in herpes labialis recurrence has not been systematically evaluated. Objectives: The aim of this study was to investigate whether repeated lip augmentation with HA filler is associated with changes in the incidence of RHL episodes over time. Methods: A self-controlled longitudinal observational study was conducted in adult patients with a documented history of RHL undergoing lip augmentation with HA filler between 2016 and 2025. Each participant served as their own control, with recurrence rates compared across predefined baseline and posttreatment intervals. The primary outcome was the incidence of clinically typical herpes labialis episodes, expressed as episodes per person-year. Recurrent events were analyzed using generalized estimating equations with a negative binomial distribution. Results: Ninety patients were included in the final analysis. Baseline incidence was 5.22 episodes per person-year. No significant change in recurrence rate was observed after the first filler session. A statistically significant reduction emerged after the second session (incidence rate ratio [IRR] 0.81; 95% CI, 0.72-0.91; Conclusions: In this longitudinal self-controlled cohort, repeated lip augmentation with HA filler was associated with a progressive reduction in RHL incidence after multiple sessions. The clinical relevance of this observed reduction was not predefined. Although causality cannot be established, the temporal pattern and statistical robustness of the findings warrant further investigation. Level of Evidence 4 Therapeutic: