I had been struggling with itchiness from head to toe for two months. My symptoms have gone away after about a week, thanks to my doctor. He recommended the following.
1. Take cooler showers (as cool as you can tolerate), and apply baby oil ($3.50 for a big bottle) to the itchy areas immediately after showering and before drying. Pat your skin dry gently, and don't rub the towel over your skin.
2. Use a humidifier to keep room relative humidity at 55-60%. I bought a Crane. It works very well and is nearly silent.
3. Use hydrocortisone 2.5% cream on problem areas as needed. This requires a prescription. I only needed to use it once or twice.