You need to see a dermatologist...
"Skin conditions like dermatitis, lice, scabies and hives, internal diseases like liver and kidney disorders, diabetes, iron deficiency anemia, irritation and allergic reactions to chemicals, wool, soaps, cosmetics and certain foods can cause itchy skin.
You can take some antihistaminic like Benadryl or Claritin. Also apply some Corticosteroids, such as hydrocortisone cream on the itchy areas. A well-balanced diet that includes carbohydrates, fats, minerals, proteins, vitamins, and liquids will help to maintain skin health. You should take a comfortably cool bath and wear smooth-textured cotton clothing. You should choose mild soaps without dyes or perfumes and use a mild, unscented laundry detergent when washing clothes, towels and bedding."
www.medhelp.org/posts/Dermatology/Full-body-itching/show/1140838