Why does acne occur?

Hormonal changes at adolescents trigger increased sebum production. Sebum is a kind of oil produced by skin to maintain its moisture content. Excess sebum can clog the skin pores. Propioni bacteria acnes, is normally present over skin, overgrows in areas with high sebum and releases mediators that lead to inflammation of skin. Minimal inflammation increases thickening of the lining of pores and finally blockages resulting in blackheads and whiteheads. Increased inflammation may lead to a deeper blockage in the pore causing a raised skin lesion (pimple) and an even deeper blockage can cause painful bigger skin lesions- nodules or cysts, the most severe acne lesions. Nodules and cysts very often result in pigmentation and scarring and require early treatment. While a simple pimple may or may not leave pigmentation and the pigmentation left behind by them is milder and tend to resolve faster. The whiteheads if improperly removed cause ice pick scars and hence should avoid removing them. Sometimes in trying to remove whiteheads, one actually ends up irritating the pore causing more inflammation and bigger pimples.
Please do not rupture or squeeze your pimples.
Minimal handling of the skin with pimples is advised.
Nodules and cysts require early treatment.