Dermatologists find that there are a few factors that combine to create blackheads. Excess oil production is a big one, especially when the seasons change. Dead skin buildup or heavy, pore-clogging skincare products can result in blockage. So can hormonal fluctuations due to stress or poor sleep.
When oil and dead skin accumulate faster than your skin sheds them naturally, pores become congested. If the clog stays beneath the surface, it becomes a whitehead. If it opens to the air, it becomes a blackhead.