What is it?
Blackheads are small dark bumps that appear on your pores. As your pores open, dead skin cells, dirt and sebum tend to clog them. If the skin around a clogged pore stays open, the clog is exposed to the air, which makes it black. Usually, blackheads appear on your T-zone (nose, forehead and chin).
Origins & main causes
Any factor that can increase your oil levels can increase the amounts of blackheads on your skin. Heat and humidity can open your pores and make them welcome impurities with open arms. A poor air quality and high pollution levels also increase your chances of having blackheads, as it means more impurities filling up your pores.
What to do
Wash, exfoliate and look for oil-free or non-comedogenic products. Some ingredients that can help purifying your skin would be charcoal or clay. The key is trying to eliminate excess oil, dead skin cells and dirt from your pores.