Why my body itches when my body is warm?!!?

Everytime i did something like drinking hot Milo or just do something that makes my body hot IT ITCHED like HELLLLL ..it felt like a millions of tiny needle poking throughout my whole body . from head to toe . i shower twice a day with Dettol and still same result. OR could it be my 20 years old bed. D= !@#@%%&()(&*(#!@!$#$^%* ???????!!!!!!!! AH?