Paradoxically, stress and sweating can also increase the itchy sensation. A drastic answer is to move to a more humid climate. Try to keep room heat turned down. Reduce duration, temperature and frequency of showers or baths reducing overall bathing to two times per week with daily sponge baths between. All soaps are drying.
Bath oils can be helpful.
Soaps and lotions without scent are preferred. Avoid fabric softeners. Use scent-free detergent like Woolite or Ivory Flakes, and use an extra rinse to eliminate residue. Wear soft, loose cotton or silk clothing next to skin. Avoid tight clothing that rubs.