Why trust NBC Select? Blackheads, also known as open comedones, start as sebum plugs, which are collections of oily liquid that help the skin stay lubricated. They clog up pores when they mix with ...
They can form when excess oils and dead skin cells build up and block a pore, creating a small sebum (oil) plug at the opening of the pore ... while azelaic acid decreases excess production of keratin ...