Question: what are causes of oily skin?
Answer: Genetics. If your mom or dad have oily skin, it's likely you will have inherited the trait. ... 
Environment. Humidity and hot weather tend to stimulate the secretion of sebum, leading to more oil on the skin. ... 
Over-Washing. ... 
Medication. ... 
Cosmetics. ... 
Hormonal Changes. ... 
Poor Diet. ... 
Prevention or Treatment?