Hi greetings. Well it's tough to say the exact cause of itching without seeing her or without detailed history. What I could suggest is use of a moisturiser daily like emoderm cream - should be applied two to three times daily. Also for the black mark which may be a lichen simplex chronicus - will require treatment with TCS cream. See a dermatologist near you. Hope this helps. Warm regards Dr Govind Suresh Mittal.