Cutting and Brushing Hair on Shabbos

Cutting or Detaching Hair

Due to the melacha of ‘gozez’, shearing, it is forbidden to cut or detach even one hair from anywhere on one’s body. It is a Torah prohibition to do so with an implement or depilatory powder or gel and a Rabbinic prohibition to do so by hand or with one’s teeth (SA 340:1, MB 1, 2, SSK 14:47).

It is permissible to rub or run one’s hands through one’s hair on Shabbos, as long as one does so in a manner that does not inevitably detach hair (SSK 14:48). (SSK 14:48).

it is forbidden to comb or brush one’s hair with regular combs and brushes on Shabbos as they will inevitably detach hair. Such combs and brushes are therefore muktza.
Special brushes: it is, however, permitted to brush one’s hair with a brush with soft bristles and one may also use a comb which has very large spaces between teeth, as it is not inevitable that these will detach hair. It is preferable to designate such brushes and combs for Shabbos, to avoid any concern of ‘uvdein dechol’, looking like one is doing a weekday activity (SA 303:27, MB 87, SSK 14:50).
Mikva: a woman who is going to mikvah on Friday night and forgot to comb her hair before Shabbos should consult a Rav for guidance, given she may not now comb her hair (SSK 14:51).

It is appropriate not to brush a sheitel on Shabbos in a regular fashion with a normal brush, as it is problematic to detach hair from it (whilst there is no prohibition of ‘gozez’, shearing, as it is not part of the body, the poskim discuss other possible prohibitions including koreia – tearing and mattir – untying).
Soft Brush: One may, however, smooth it out with a brush with soft bristles, as this will not inevitably detach hair. Such a brush should preferably be designated for Shabbos use.
Brushing Gently: Some are lenient to permit one brush the sheitel gently with a regular hairbrush, in particular if it can be done in a manner that hair will not inevitably be detached (which can depend on how the sheitel is made). As above, this should ideally be done with a brush designated specifically for Shabbos use, which will also circumvent any issue of a hairbrush being muktzah (alternatively, if it is designated specifically to brush sheitels it will also be OK so long as it doesn’t inevitably detach hair).
Very Tangled Hair: If the sheitel hairs are very tangled, such that the brushing is needed to make it suitable to wear, this is forbidden even if hair won’t be detached, due to ‘tikkun maneh’, fixing. (SSK 14:52, PT 303:18, fn 115, Shalmei Yehuda 10:3).

if one has a plaster stuck on a hairy area of the body, it is preferable not to pull it off on Shabbos as this will inevitably detach hairs from the body; if through the use of substances such as oil etc (being mindful of any concerns of muktza and memareiach) one can loosen the adhesive to the point where it is not inevitable that hair will be detached, one may then remove the plaster.
In cases where the plaster is causing distress, however, one may be lenient to remove it even if hair will be detached, given that it is consequence one has no interest in, is destructive, and ‘kileachar yad’ (not the normal way of detaching hair) (SSK 35:30, fn 78).

One should refrain from removing lice from hair on Shabbos, lest one detach hair or kill the louse (SSK 14:59).