Longitudinal Changes in Systemic Total Oxidant Status Following High-Intensity Focused Ultrasound for Facial Rejuvenation: A Prospective 6-Month Controlled Pilot Study

High-intensity focused ultrasound (HIFU) is widely used for non-invasive facial and neck rejuvenation; however, its longer-term systemic biochemical effects remain insufficiently characterized. This prospective controlled pilot study investigated longitudinal changes in systemic oxidative status at baseline and 3 and 6 months following a single HIFU treatment. Thirty healthy adults were enrolled, including 25 participants who underwent facial and neck HIFU and 5 untreated participants serving as a comparison group. Serum total oxidant status (TOS) was quantified using an enzyme-linked immunosorbent assay (ELISA)-based method, and longitudinal changes were assessed using mixed-effects modeling. Baseline TOS did not differ significantly between groups (19.54 ± 1.49 vs. 19.78 ± 1.81 μmol/L; p = 0.794). A significant group × time interaction was observed (Wald χ2(2) = 21.78, p < 0.001). Within the HIFU group, TOS decreased at 3 months (17.31 ± 1.51 μmol/L; Bonferroni-adjusted p < 0.001) and remained below baseline at 6 months (18.34 ± 0.95 μmol/L; p < 0.001), despite a partial increase between 3 and 6 months (p = 0.002). Three participants (12.0%) reported mild, transient deep-tissue tenderness; no serious adverse events occurred. Overall, HIFU was associated with a distinct longitudinal TOS pattern, supporting further investigation of redox and tissue-remodeling biomarkers.