What can cause dry, itchy, scaly skin that seems to be spreading on different parts of my legs?

Diagnosing rashes: Correctly diagnosing a rash requires a good history and a physical exam. You could have dry skin, atopic dermatitis, contact dermatitis, a dermatophyte infection or a large number of other diagnoses. To get a diagnosis of any rash, you really need to see a physician. Start with your primary care doctor, and consider a dermatologist if s/he isn't sure what to recommend..