Standard nezirus is for thirty days. [If] he shaved [his head], or [if] bandits shaved it, he forfeits thirty days.  A nazir who shaved, whether with a scissors or with a razor or by plucking a minute amount, is liable.  A nazir may rub or scratch [his head], but he may not comb it. R’ Yishmael says: He may not rub it with earth since it causes the hair to fall out.