I keep getting blackheads. What causes them?

I keep getting blackheads on my cheeks and around my nose, so I'm trying to figure out what's causing them. I think I wash my face thoroughly, but they still keep coming up. I've heard that excessive sebum production is a common cause of blackheads, but I'm confused because I have dry skin and they still appear. I've heard that dead skin cell buildup is also a cause of blackheads, so I'm trying to manage it, but I'm not sure if it's working. If you know a solution, please advise!