Since blackheads are your main concern, let's limit our discussion to how we get them, and how we treat them. Dead skin cells that are naturally due to be shed off, or exfoliated, also exit through the pores. A clog can occur in the facial pore if too much sebum gets produced, and it can't all get out of the pore fast enough, or if some of the shedding skin cells get stuck in the pore's opening to the air. Or, a combination of both can occur and lead to a clogged pore. Which ever way, this clogged pore is seen visibly as a blackhead.
Blackheads appear as tiny black dots on the face that are very difficult to see.
Probably the best thing to do is see your dermatologist. Treatment of blackheads revolves around unclogging the pore, so whatever is stuck there gets out. Many people think scrubbing, or washing your face can unclog the pores, but this is not true. Think of your clogged pore as a clogged drain in a sink. Salicylic acid containing products are over the counter pore uncloggers, but they are relatively weak.