It seems like a case of Xerotic eczema
to me,the most important thing in controlling this type of eczema is to keep the area moisturised,to avoid very hot and cold shower,frequent washing and harsh perfumed soaps or body shower products.
Kindly keep the area moisturised with white petroleum jelly and use non perfumed and mild soaps for baths. In between you can use Topical steroids
and sedating anti histamine
25 mg once before going to bed.
I am sure these measure will prove helpful but if not then you have to do some blood tests like liver,renal and thyroid function tests
along with a full blood count to exclude internal causes of the itch because its not always the local(environmental) causes which result in itch.
I hope you ll be benefited from the discussion.
All the best.