Causes
Pimples happen when pores become clogged with sebum and dead skin. Sometimes this leads to infection and inflammation. Why they affect some people more than others is largely unknown.

The sebaceous glands and pimples

The sebaceous glands are tiny skin glands that secrete sebum, a waxy or oily substance that lubricates the skin and hair.

Sebaceous glands are found inside the pores of our skin, all over the body, except the palms of the hands and soles of the feet. There are more sebaceous glands on the face and scalp than elsewhere.

As the glands produce sebum inside the pores, new skin cells are constantly growing, and the outer layers of skin are being shed.

Sometimes, dead skin cells are not shed. They remain in the pores and get stuck together by the sticky sebum, causing a blockage in the pore.

Pore blockage is more likely to occur during puberty, as the sebaceous glands produce more sebum at this time.