Several factors are involved in the development of acne. Central to this are the sex hormones, which are produced at puberty. The male hormone testosterone - found naturally in women as well as in men - triggers the sebaceous glands to produce more of an oily substance called sebum, making the skin more greasy. However, most acne sufferers don't have a hormone problem and their hormones are at normal levels in their blood.

When there is an excess of sebum, the area around a hair follicle and the opening through the skin - the pore - can become clogged. A bug, a bacterium called Propionobacterium acnes, that lives normally on the skin , can thrive within the blocked pore. This infection causes inflammation, which is responsible for the redness and swelling of a spot. Sometimes as in severe acne, the pocket of inflammation witin a pore can rupture, causing damage to the skin that can result in scarring.

Microcomedone