Acne is an overproduction of sebum and elimination of dead cells; accelerated and in higher quantities than the pore can cope with. This situation then causes a plug full of bacteria to form that clogs the pore. It causes whiteheads, pimples in the dermis. Being the mildest and non-inflammatory form. The next level is the typical pimples and papules. Some pink bumps that can hurt when touched. Then pustules – red pimples with pus – and nodules – large, painful, solid internal boils – appear.  Or in some people they manifest as deep, pus-filled cysts.