Pore size is genetic, but pores can enlarge over time due to congestion and sun damage. When pores are clogged, they will be stretched and appear larger.
Enlarged pores due to sun damage are caused by damage to collagen. Free radical damage from UV exposure, pollution, and smoking will all damage collagen and make it less robust. This leads to pores expanding like a drawstring bag.
For enlarged pores that look like doughnuts, these may be benign spots of sebaceous hyperplasia representing overactive oil glands.
For congested pores, products with beta hydroxy acids, which dissolve in oil, natural clays will clear out pores and help to keep them clear. Thorough cleansing with balm cleanser is also essential since oil dissolves in oil better than in water.
Laser treatments that stimulate collagen are very effective at decreasing pore size. A study of the Clear+Brilliant fractionated non-ablative laser involved painting subjects’ skin with fluorescent dye, then wiping it off the surface so that it only remained in the pores, and then photographing with high resolution during a series of treatments. Six treatments produced clinically and statistically significant improvement in pore size in those treated.