Itching on arms and back and legs and stomach. no visible rash or bumps. no major changes in diet. what are the probabilities ??

Too numerous to list: NOT FOOD. Itch without a rash is very difficult to define. You may need some tests. When you go to the dermatologist, bring all pills, vitamins, anything you swallow or apply. Sometimes this is due to underlying disease, so you should not delay.

Rashless itching: Many possibilities: photoallergic reaction from medications or foods; dry skin from too hot baths/showers; dryness from harsh soaps (e.g. Ivory), laundry detergents, fabric softeners (especially dryer sheets); use of vitamin A gel/cream/lotion dries skin. Sometimes anemia can manifest as itching. Review meds/supplements/soaps/ fabric softeners/cologne; discuss w/ FP/dermatologist. Zyrtec (cetirizine) may help