Acne occurs when your hair follicles( pores) become plugged with oil and dead skin cells. Our skin has oil glands which secrete an oily substance known as sebum to lubricate your hair and skin.
When your body produces an excess amount of sebum and dead skin cells, the two can build up in the hair follicles and form together as a soft plug, creating an environment where bacteria can thrive.
This plug may cause the follicle wall to bulge and produce a whitehead. Or, the plug may be open to the surface and may darken, causing a blackhead. Pimples are raised red spots with a white center that develop when blocked hair follicles become inflamed or infected. Blockages and inflammation that develop deep inside hair follicles produce lumps beneath the surface of your skin called cysts.