Polyquaternium 10 offers glide, silkiness and a conditioned feel, making hair more manageable with less frizz static. It is naturally derived Hydroxyethylcellulose.
The Environmental Working Group (EWG's) Skin Deep is the world's largest personal care product safety guide. They rate ingredients according to their hazard score on a 0-10 scale from low to high hazard. For example, they give water a score of 0.
Accordingly they have rated Polyquaternium 10 with a score of 1.