Many dogs bleed when they are chewing on a hard bone or treat, including rawhide, for a long time. When you notice their tooth or gum bleeding, the intelligent thing would be to take away rawhide and not let them chew on anything else, at least for a day.  However, if chewing rawhide results in bleeding gums several times, it is essential to consult a vet and avoid giving them the treats for a few days. Also, we would recommend you replace rawhide with a softer chew treat for them.