Touching Hair - Washing Hands

As is known, someone who for example brushes their hair with their hand is required—according to the Shulchan Aruch—to wash their hands afterward.My question is: what exactly is considered “touching the hair”? Does merely touching the top layer of hair (like people often do when adjusting their hairstyle) also require washing, or is it only when one runs their fingers through the hair?

Shalom UvRacha,

Only someone who touches deep inside the hair needs to wash their hands 

But one who touches only the surface of the hair does not need to wash his hands.