Itchy skin that isn't accompanied by other obvious skin changes, such as a rash, is most often caused by dry skin. Dry skin usually results from environmental factors that you can wholly or partially control. These include hot or cold weather with low humidity levels, long-term use of air conditioning or central heating, and washing or bathing too much. I have extremely itchy skin and it can be anywhere for me including my abdomen.
Other conditions cause itchy skin as well. Skin disorders, internal diseases, allergies and drug reactions top the list.
You may want to mention this to your physician. I use a lotion recommended by my Dermatologist, AMLACTIN, moisturizing body lotion. It is one that works really well for dry feet to if anyone has that problem.