What Causes Large Pores? Most often, genetics determine who will have large pores. Other causes for large pores can be oily skin, since excess oil sits around the skin’s pores, making them appear enlarged. Oily and unclean skin can also cause oils to settle around the pores, making them appear larger as the skin around them thickens. Skin thickens, too, from sun damage and aging as cells build up around pore openings. Ironically, rather than hiding skin imperfections, makeup can actually cause pores to appear enlarged, especially when it’s not properly washed off. It can also settle in and around pores to highlight instead of hide them. But mostly, cosmetics can be a magnet for dirt and oils, causing large pores to, quite literally, shine. Blackheads may not cause large pores, but they are an undesirable result of them, a result of dirt settling into large pores and — given their dark color — being especi