Delayed Adverse Subcutaneous Reaction to a New Family of Hyaluronic Acid Dermal Fillers With Clinical, Ultrasound, and Histologic Correlation.

Hyaluronic acid (HA) is considered the safest filler due in part to its supposed low risk of immunogenicity and to claims of reversibility with hyaluronidase. Over the past years, the industry has tried to create more differentiated and longer-lasting products by modifying the chemical structure of