I have had itching from head to toe in the past 4 weeks. it started on my legs. it can itch anywhere now but spreads. few minutes later, disappears.

Many causes: There are many causes of itching. It can be as simple as dry skin or as complicated as liver disease. It can be from allergies. You could certainly try a non-sedating antihistamine like loratadine and see if that helps. Since it has been going on for a month iti s probably a good idea to see a doctor and have your liver function tests checked just to make sure they are normal.