What you seem to be having is seborrheic dermatitis. Seborrheic dermatitis is a common skin condition that causes flaky,dry, white to yellowish scales to form on oily areas esp under the nose or anywhere on face.
Treatment usually involves use of antifungal, anti inflammatory and sebo suppressive or Keratolytic ingredients. Dermatologist also recommends the use of photodynamic therapy which involves the usage of UV- A, UV- B laser and red or blue LED light to inhibit the growth of the yeast and reduces the inflammation.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.