What Is The Treatment For Itchy Skin?

hi. For the last 2 weeks i have been experiencing itchy skin, mostly on my arms and legs but there is no visible rash or redness and my skin is not dry, at the same time i have been quite light headed. I work in a hospital and when observing theatre after 10 minutes of standing still, i feel very light headed and if i dont sit down i feel i will faint. I have a very healthy diet. I have been prone to fainting and light headedness over the last 5 years, My doctor has been unable to identify any problems and i have just succumb to carrying a snack with me for when i start to feel 'funny'. I am 20 and believe myself to be healthy
Thanks Abi