South Asian Journal of Research in Microbiology

Understanding the immunological responses to hyaluronic acid (HA) as cosmetic fillers is essential for optimizing patient safety and outcomes. Although HA closely resembles endogenous human HA, variations in molecular size, source, and potential contaminants can provoke both innate and adaptive immune response. HA injections have the potential to activate both short-term and long-term immune system reactions. The immune reaction ranging from mild, self-limited swelling to severe delayed inflammatory responses. The biofilm-forming skin bacteria and the proinflammatory properties of low-molecular-weight HA can complicate the clinical picture. Therefore, careful patient selection, pre-injection sensitivity assessment, and adherence to meticulous injection techniques by trained specialists are crucial. Ongoing research into the mechanisms of immune activation and improved diagnostic strategies will enhance the safe use of cosmetic fillers and help clinicians effectively manage and prevent adverse reactions. Hyaluronic acid fillers closely resemble natural HA but can still trigger serious immune responses but the delayed-type hypersensitivity reported to be the most common consequences. To minimize risks and ensure patient safety, specialists should perform injections with prior sensitivity testing.