Pores are small hair follicle openings in the skin that release oils and sweat. Large or enlarged pores are more visible. Enlarged pores are commonly found on oily or aging skin and can get clogged with debris and oils, like sebum, that should flow out of pores.
Most often, genetics can be the cause of large pores. Some people just naturally have invisible pores, and some people are prone to having larger pores. If you are genetically prone to larger pores, maintaining a good routine and treatment program is important. The other contributing factor is cellular debris, which dead skin cell build up. Oily and unclean skin can cause oils to settle around the pores, making them appear larger as the skin around them thickens. Skin also thickens from sun damage and aging as cells build up around pore openings. As skin ages, cell renewal activity and collagen production decreases, thereby increasing the appearance of visible pores.