I have what sounds like the same thing, my dermatologist
told he it was pityriasis rosea
or Christmas tree rash
. It starts with a 'herald patch', the large dry patch that is still present... Then a couple weeks later (or a couple days depending on the person) you will see a bunch of smaller pink dry patches that form sort of a Christmas tree shape, though mine looks like blobs. The Dr. said it was viral and it usually starts with a sore throat
as a symptom in most people. The rash usually goes away in 6-8 weeks. Take antihistamines and keep the area moist to calm the itching (if it is itchy for you).