Hyaluronic acid - What's the source? Is it made by chemical process or obtained from animals?

Some brands of Hyaluronic Acid are made out of rooster combs (Hyalgan). Other brands are made from a bacteria called Streptococcus equi bacteria (Juvederm). Both are very pure. Neither are very likely to cause any allergic reaction. Both are very safe. Juvederm tends to last longer so I don't use much Hyalgan anymore.

I have NEVER seen an allergic reaction to Juvederm, Restylane, Perlane or Hyalgan. I have read about only 1 single case of an allergic reaction, which got better with treatment. Overall, I think these products are safe for injection into the face, especially into the smile lines (the nasolabial folds). Other sites are a bit riskier, but an experienced injector should be able to provide very safe facial injections with any of these products.