Large pores are mainly a result of genetics, but there are other factors that may contribute to an enlargement of pores overtime: excessive sebum production, skin debris, cystic acne, and aging. Though you cannot “shrink” pores, there are treatments available that can reduce their appearance. Depending on the cause of the large pores, various treatments that help clear clogged pores, increase skin elasticity, and increase collagen production can all be useful in creating a smooth, “poreless” finish.