Histology of the Host Response
Microscopic analysis of filler sites reveals how the body interacts with different materials. HA fillers typically appear as "lakes" of basophilic material with minimal inflammatory cells. In contrast, biostimulatory fillers like PCL (Polycaprolactone) or PLLA show a predominance of lymphocytes and multinucleated giant cells surrounding the microspheres.
This "foreign body response" is essential for the product's function, as it is the very mechanism that drives the production of new connective tissue.
The most severe risk in dermal filler application is vascular occlusion, where filler is accidentally injected into an artery. If not addressed, this can lead to skin necrosis or even blindness.
Prevention: Practitioners use slow injection speeds, low pressure, and blunt-tipped cannulas in high-risk zones (like the glabella or nose).
Intervention: For HA fillers, the enzyme hyaluronidase is injected immediately to dissolve the gel and restore blood flow. For non-HA fillers, management focuses on vasodilators and anti-inflammatory protocols.