Understanding delayed-onset inflammatory responses (DIRs) to hyaluronic acid fillers: a comprehensive literature review and retrospective cohort study.

This study aims to investigate the underlying mechanisms and triggers of delayed-onset inflammatory responses DIRs after hyaluronic acid (HA) fillers injections. The literature review included articles on DIRs following HA filler treatments and identified immunological triggers, bacterial contamination, and filler degradation as key factors contributing to DIRs. Additionally, patient data were analyzed from patients treated for DIRs and showed possible immune activation events prior to DIRs included flu-like symptoms. This study underscores the complexity of DIRs following HA filler treatments and the need for transparency from manufacturers. Comprehensive ingredient data are crucial to better understand DIRs and ensure patient safety.