211:12 A mourner may not cut his hair for the entire thirty days of shloshim – not the hair on his head, not his beard, nor anywhere else. If he is in mourning for a parent, he may not have it cut until his friends criticize him for his shabby appearance. The authorities disagree as to the degree of rebuke necessary to permit haircutting. The practice is not to cut it for the entire twelve months unless necessary. For example, if the mourner’s hair became a burden to him, or if he works with non-Jews and he would disgrace himself because of his hair, then he may cut it. He doesn’t need explicit rebuke from his friends about his appearance; it is sufficient that his hair has grown to a point where it’s different enough from everyone else’s that they might start commenting on it. In such a case, the mourner may cut his hair so long as it’s after the thirty days.
211:13 Just as a mourner may not cut his hair the entire thirty days, he likewise may not cut his nails with an implement; to do so with his hands or teeth is permitted even during shiva. Even if the mourner is a mohel, he may not trim his nails to perform the priah (part of the circumcision) unless there is no other mohel available. If that’s the case, then he may trim his nails even during shiva. A woman in mourning whose time to go to the mikvah arrived after shiva but during shloshim may ask a non-Jewish woman to cut her nails. If no non-Jewish woman is available, a Jewish woman may do it for her.