It seems that you may be having seborrheic dermatitis
There may be flakes or mild greasy scales on scalp,paranasal areas of face,eye brows,ears,axillae,chest and groin areas..all seborrheic areas.
There is exact no cause. There may be diathesis to develop SD.
,weather,sunrays..etc may precipitate the disease.
Yeast like pityriasis ovale may be responsible.
Take anti fungal like ketoconazole
Apply mild steroid with clotrimazole
Do shampoo with ketoconazole containing shampoo.
If needed,take short course of steroids.
You maybe benefitted .
I hope you got my answer.
Dr. Ilyas Patel MD