How to differentiate clogged pores or open pores?

Clogged vs open pore: Open pores are normal. Some opens are small while others are large. Some topical treatments like AHA's can help reduce the size of open pores. Clogged pores have something stuck in them. Usually sebum, the normal substance that the glands produce. If it becomes dry, it makes a plug. Skin can also grow over the exit to the pores blocking them. Looking at them is enough to make the diagnosis.