How to tell human hair from synthetic hair?

A : Human hair has natural protein . It is easy to tell by burning and smell: human hair will be ash, which will go away after pinching. Human hair will smell foul. When burning, the human hair will show white smoke.

While synthetic hair will be a sticky ball after burning and will show black smoke.

Moreover, human hair may have very little gray hair and split ends. It is normal but not a quality problem.