1) If in the middle of one’s meal one touched a part of the body which is generally covered, or scratched one’s scalp etc. one must wash one’s hands again. Even if he has bread in his mouth, he may not swallow it before washing his hands. However, he does not make a Berachah on this washing. (Shulchan Aruch and Mishne Berura 163)

2) If one touches one’s hair without scratching, one is not obligated to wash one’s hands. (ibid)