The incidence of ischemic complications in HA fillers is approximately 0.3%. The best way to prevent tissue necrosis is through a thorough knowledge of facial vascular anatomy and a meticulous technique. Necrosis occurs due to arterial or venous obstruction. Late complications are defined as those that appear after approximately 2-6 weeks.
They include late allergic reactions, chronic inflammation and infection, granulomas, migration of fillers, loss of function, telangiectasia, and hypertrophic scars. A detailed history may reveal a possible allergy. To avoid infection, the injection site should be thoroughly disinfected and degreased, and the injection should not be done with makeup. The infection should be treated immediately with antibiotics and usually responds quickly.
The formation of granulomas is unpredictable, but it depends on the material used. Particulate material is prone to induce a macrophage reaction, particularly permanent fillers, but also poly-L-lactic acid (PLLA) whose particles have a crystalloid structure. The probability of granulomas increases with the surface-volume ratio of filler particles and their shape with sharp edges. Good quality hyaluronic acid fillers practically lack this effect.
Silicone oil causes a slightly different reaction called siliconoma with lymphocytic infiltrates. Permanent fillers based on acrylate gels appear homogeneous but, in fact, they are particulate. The most serious complications are vascular. Vascular occlusions can lead to necrosis (tissue death), scarring and, even more seriously, blindness.
In fact, dermal fillers have already resulted in 98 reported cases of blindness (Beleznay et al, 201.Side effects reported in clinical trials include facial weakness, drooping of the eyelid and drooping of the eyebrows). Other side effects included localized pain, swelling, redness and bruising at the injection site. Rarely, injections have caused double vision, dry eyes, or difficulty swallowing or breathing. It is not recommended to inject botulinum toxin products for cosmetic purposes during pregnancy or lactation.