Three Acne Causing Factors

1) Abnormal keratinization of the lining of the sebaceous glands caused by androgen stimulation, resulting in plugging of the gland.
2) Increased production of sebum by the sebaceous gland due to androgen stimulation.
3) A bacterium, Propionibacterium acnes, proliferates within the gland and modifies the sebum. Propionibacterium acnes is a bacterium normally found on the skin.

The plugging of the gland and the action of the bacterium cause an intense inflammatory reaction, resulting in a blackhead (open comedone) or a whitehead (closed comedone). The color of the blackhead is due to melanin granules and is not dirt. Continued plugging and inflammation lead to the pustules (pimples), papules and cysts of acne.