Whiteheads result when the pore is completely blocked, trapping oil, known as sebum, beneath dead skin cells. They become red and inflamed because of bacteria, known as P.acnes.
Blackheads are caused when the pore is only partially blocked. It is a myth that the black colour that gives them their name is caused by dirt. This is actually caused by the skin’s pigment, known as melanin, reacting with the oxygen in the air.
Papules appear as red, inflamed bumps on the skin. They have no head.
A pustule appears as an inflamed, red spot with a white or yellow centre
Nodules occur with severe acne and appear as large, hard bumps under the skin’s surface. They can often result in acne scars.
Acne cysts occur in cases of severe acne and are effectively pus-filled nodules. They can be painful and commonly result in scars.