Is borax safe to bathe in for scabies?

Almost certainly but. As is often the case with natural remedies, no formal research has been done on the safety of bathing with borax but as best as i can tell it appears to be quite safe when use this way. See http://www.Crunchybetty.Com/getting-to-the-bottom-of-borax-is-it-safe-or-not for many detailed discussions by those who have tried borax baths see http://www.Earthclinic.Com/remedies/borax_questions.Html.