Background and Objectives: Hyaluronic acid (HA) dermal fillers are among the most widely used injectable materials in esthetic medicine. They are generally safe, but delayed inflammatory reactions (DIRs) have been observed, particularly after viral infections or vaccinations. Such events have raised questions about the role of immune activation in filler-related complications. This review examined the available literature on DIRs to HA fillers that occurred in the context of viral illness or immunization, with attention to how these reactions present and how they are managed. Materials and Methods: A systematic search was carried out in PubMed, ScienceDirect, ClinicalKey, and Google Scholar between October and November 2024. Only human case reports and case series were included. The protocol was registered in PROSPERO (CRD420251030918), and study quality was assessed using the Newcastle–Ottawa Scale. Results: Six publications met inclusion criteria: four case series and two case reports, describing 25 women between 22 and 65 years of age. Patients developed swelling, erythema, angioedema, or, in severe cases, marked facial edema after HA filler injections, with symptom onset ranging from several hours to several weeks following viral exposure. Corticosteroids and hyaluronidase were the most common treatments, though milder cases sometimes resolved without intervention. Study quality varied, with some reports providing limited detail on patient characteristics and follow-up. Conclusions: DIRs associated with viral infections or vaccinations remain uncommon but clinically relevant complications of HA filler use. Limited case-based evidence indicates potential effectiveness of corticosteroids and hyaluronidase, though management practices remain inconsistent. Larger prospective studies are needed to clarify underlying mechanisms and to establish standardized guidelines for treatment.

Background: Botulinum toxin type A (BoNT-A) has been proposed as an adjunct to orthognathic surgery because its temporary neuromuscular effects may reduce muscular loading during postoperative healing and potentially influence fixation stability, skeletal relapse, and postoperative recovery. This systematic review aimed to evaluate the available clinical evidence regarding the adjunctive use of BoNT-A in orthognathic surgery. Methods: A systematic literature search was conducted in PubMed, the Cochrane Library, and Google Scholar in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Clinical studies directly comparing orthognathic surgery with and without adjunctive BoNT-A administration and reporting outcomes related to mechanical stability, skeletal stability, or postoperative recovery were included. Risk of bias was assessed using the Cochrane Risk of Bias 2 (RoB 2) tool for randomized controlled trials and ROBINS-I for the non-randomized study. Results: Three studies met the eligibility criteria, comprising two randomized controlled trials and one retrospective comparative study. Considerable heterogeneity was observed in surgical procedures, targeted muscles, BoNT-A doses, timing of administration, and evaluated outcomes. Individual studies reported associations between BoNT-A administration and a lower incidence of fixation plate fracture, reduced anteroposterior skeletal relapse at the Pogonion, or lower preanalgesic pain scores and postoperative opioid consumption. However, these findings were derived from different studies evaluating distinct interventions and outcomes and were not consistently demonstrated across comparable outcome measures. Conclusions: BoNT-A may represent a promising adjunct to orthognathic surgery, with potential benefits for fixation-related mechanical stability, selected parameters of skeletal relapse, and postoperative pain management. However, the limited number of studies, methodological limitations, and substantial clinical heterogeneity preclude definitive conclusions. Further well-designed randomized controlled trials with standardized injection protocols and longer follow-up are required before routine clinical use can be recommended.