Many women have a false impression that hair serums should be avoided because they can flatten fine hair. This is true, for the wrong kind of serum which can leave behind a sticky residue or cause an itchy scalp from serum build-up. The right kind of serum can be used every day even on thinning, graying, or wispy tresses. A lighter serum smooths and hydrates rough hair cuticles, nourishes the scalp, decreases frizz, and gives you a silkier, smoother mane.