White spots in back of elbow (size of 0.5cm x 1.5cm) 2week duration?

See a dermatologist: Get this looked at. This is the sort of thing which cannot be diagnosed without an examination of the lesions. Good luck.

Psoriasis : Or other similar condition comes to mind. Otherwise any answer is a guess without a picture or without being able to feel the texture of the skin lesion. Start by seeing a family doctor or internist. See a dermatologist is the problem persists and your doctor's diagnosis is "skin rash".