Suggest Remedy For Insect Bite

A girl spent the night at my house and brought lice into our house and so we sent her home and told her parents about it and we all did treatments and cleaned our house really good.Then our pets got it and we treated them. when we were all done with this it came back but now only the pets and me and my mom have it and they are bitting our skin and head and everywhere.this has been going on for 5 weeks now and nothing has helped.Please help