Do facial fillers cause cancer?

Thank you for your question. 
There is no evidence that Hyaluronic acid fillers cause cancer. Hyaluronic acid is a component that is part of our own tissue structure and there is no reason to assume that this will result in triggering a reaction to develop cancer. 
Cancer development is a multifactorial process and no one thing can solely be 'the cause.' Hyaluronic acid occurs naturally in skin and cartilage. There are studies to show it has a treatment benefit in patients who have radiotherapy in prostate cancers. Studies have shown that the overall radiotherapy dose can be reduced. 
Your body has enzymes that break down hyaluronic acid so whatever is used, your body has the ability to break it down. 
I hope this is helpful for you
Kind regards 
Rohit Seth 
Plastic, reconstruvtive, aesthetic and hair transplant surgery

There are several different types of fillers, the most prevalent is the ones made from Hyaluronic acid (HA)  This is a naturally occuring chemical in your body associated with collagen production.  These fillers have a huge and long safety profile based on the many years and thousands of times these products have been injected into the skin.
There is no evidence that HA facial Fillers nor the other types of dermal fillers cause cancer.