Introduction Combined platelet-rich plasma and hyaluronic acid (PRP-HA) offers a promising nonsurgical technique for tissue regeneration through synergistic efficacy and longevity effects. This study aims to investigate PRP-HA’s efficacy and safety for neck rejuvenation. Methods This 32-week prospective trial enrolled 30 Thai participants with mild-to-moderate neck aging. Treatment consisted of three monthly intradermal PRP-HA injections to the anterior neck surface, with follow-ups at 2 weeks, and 1, 2, 3, and 6 months posttreatment completion. Assessment included skin firmness, elasticity, biometric parameters, pain scores, and adverse effects. Results Of 29 completing participants, neck skin firmness improved 54% from baseline at 3-month posttreatment completion, increasing to 65% at 6 months (p < 0.0001). While gross elasticity initially improved at 1 month posttreatment (p = 0.0217); it subsequently declined. The 6-month follow-up showed substantial reductions in melanin and erythema (p < 0.01). Sustained improvements were observed in hydration through study completion (p < 0.01). Sebum levels decreased significantly after the first two treatments and at 3 months posttreatment (p < 0.05). No significant changes appeared in skin texture, wrinkles, and brightness. Most participants reported 51–75% improvement after the third treatment, maintaining through 6 months. No severe adverse effects were reported. Conclusions PRP-HA demonstrates safe and effective improvements in neck skin firmness, hydration, and pigment and sebum regulation, with benefits lasting 6 months after three treatment sessions. However, variable effects on elasticity and modest results on wrinkles, texture, and brightness warrant further controlled trials to further elucidate and confirm its rejuvenative properties on the neck. Trial Registration This trial is registered under the Thai Clinical Trials Registry (TCTR20230212003).

Background: A novel day–night facial serum regimen combining antioxidants, hydration-enhancing agents, and bioactive compounds has been developed to address skin aging. Objective: The aim is to explore changes in skin aging parameters and assess the safety and tolerability of a day-and-night facial serum combination. Methods: In this single-arm, non-randomized, prospective, open-label study, 30 participants aged 35–55 years applied a day facial serum (DFS) and a night facial serum (NFS) for 8 weeks. Objective assessments included skin texture and depression (Antera 3D^®), elasticity and firmness (Cutometer^®), hydration (Corneometer^®), TEWL (Tewameter^®), melanin index (Mexameter^®), and brightness (Colorimeter^®). Evaluations were performed at baseline, at 1 month and 2 months after treatment start, and at 1 month post-treatment. Results: Thirty participants (Fitzpatrick III–IV) completed the study. Significant improvements in skin texture (p = 0.002) and reduction in skin depression (−22.7%, p < 0.001) were observed after 2 months. Skin firmness increased significantly at 1 month (p < 0.001) and remained elevated post-treatment (p = 0.008). The melanin index decreased at 1 month (p = 0.048), while hydration declined after discontinuation (p = 0.016). TEWL showed a significant overall time effect; however, no Bonferroni-adjusted pairwise comparison versus baseline was significant. No significant changes were observed in elasticity or brightness. Mild transient burning was the most common adverse event. Other reported adverse events included acne, miliaria rubra, oiliness, and mild itching; all were non-serious and did not result in treatment discontinuation. Conclusions: The combined DFS and NFS regimen was well tolerated and was associated with favorable changes in skin texture and firmness. Transient local reactions, particularly mild burning sensation, were commonly reported but did not result in treatment discontinuation. Further controlled studies are warranted to confirm these observations.