Polyquaternium 7 can be used to strengthen damaged hair and is an excellent conditioner for both hair and skin. It is a very good detangler and provides slip for easier wet-combing. It will add softness and shine to dry damaged hair.
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 7 with a score of 3.