HIFU and the Oxidative Echo: A Pilot Investigation of Free Radical Stress in Facial and Neck Procedures

Background: High-Intensity Focused Ultrasound (HIFU) is widely used for non-invasive facial and neck rejuvenation, promoting collagen remodeling through controlled thermal and mechanical effects. While its clinical outcomes are well established, the immediate biochemical response—particularly oxidative stress—has not been directly quantified in humans. Objective: This pilot study aimed to evaluate acute changes in oxidative stress levels following a single HIFU session in healthy adult volunteers. Methods: Nineteen healthy volunteers were enrolled; fourteen received HIFU treatment and five served as contemporaneous controls. Venous blood samples were collected at baseline and immediately after treatment (or 40 min later for controls). Oxidative stress levels were quantified using an enzyme-linked immunosorbent assay (ELISA). Pre–post differences were assessed using paired t-tests, and between-group comparisons were performed using Δ-scores and mixed-effects modeling. Results: Oxidative index values remained unchanged in controls (18.55 ± 0.57 μmol/L pre vs. 18.55 ± 0.57 μmol/L post; Δ = 0.00 ± 0.00; p = 1.00). In contrast, HIFU treatment induced a significant acute increase (19.99 ± 1.54 μmol/L pre vs. 22.39 ± 2.29 μmol/L post; Δ = 2.63 ± 2.22 μmol/L; p = 0.0007). Between-group Δ differences were significant, and mixed-effects modeling revealed a significant time × group interaction, indicating an HIFU-specific oxidative response. No adverse effects were observed, and all treated participants demonstrated immediate aesthetic improvement. Conclusions: A single HIFU session elicits an acute increase in oxidative stress, likely reflecting controlled thermal stimulation and early tissue remodeling. Longitudinal studies are warranted to assess the persistence of these biochemical changes and their contribution to long-term clinical outcomes.