What Is The Cause And Treatment For Severe Itching All Over Body?

Hi my mother is 93 years old and has developed SEVERE ITCHING head to toe so severe she cannot sleep or sit and watch tv to be comfortable she has been to primary dr, three dermatologists and an allergist! No one can diagnose her a cure, she is losing her mind from this itching, said its on her scalp and head feels very hollow when she talks? She has been so healthy for her years and was sent to hematologist a week ago and her white platelets are very low! They ordered a bone marrow test last Thursday but stated they were not sure the cause of itching. Could she possibly have something not showing on surface as she calls us her children crying from this horrible condition. Should we take her to a Infectious disease specialist??? We need help quickly!