While being strongly driven by genetics, enlarged pores are exacerbated by diverse factors, such as: Age, Ethnicity, Gender, Sebum quantity and Environmental factors such as UV or pollution.
Excessive Oil is caused when sebaceous glands release sebum, a natural protective oil that helps to keep the skin soft and supple. However, some skins produce an excessive amount of sebum. In women, sebum output and pore size increase substantially during the ovulation phase of the menstrual cycle, as increased progesterone affects sebaceous gland activity.
Loss of Firmness in the skin can also contribute to large, visible pores. When the skin loses its firmness, the pores can become bigger because the skin around them relaxes and sags, causing the pore walls to collapse resulting in a larger opening.