Acne is usually described as an inflammatory skin disease. The inflammatory response is influenced by many “on-the-surface” factors such as the overproduction of sebum (oil) and keratin by the sebaceous glands. This overproduction of oil clogs the hair follicle and leads to bacterial growth. The bacteria multiplies and causes inflammation, and the result can appear in the form of what is known as a blackhead (an open comedo) or a whitehead (if it's below the surface).

The Immediate Causes of Acne
Basically, the process of acne formation can be divided into 4 major external causes:

1) Blockage of the pore
This occurs when the epithelial cells lining the pore mature and die. The epithelial cells turn from keratinocytes to corneocytes and become flatter and tougher. These scaly, rough corneocytes block the pore.

2) Too much skin oil (sebum)
This is caused when there is a large presence of male hormones that circulate in the bloodstream. These hormones trigger the oil glands to produce excessive amounts of sebum.

3) Bacterial colonization
Clogged pores, extra amounts of sebum and certain blood toxins create the perfect environment for acne bacteria to multiply and thrive inside the microcomedo.

4) Infection and inflammation of the comedo and surrounding tissue
Certain substances found within the cell walls, where the bacteria multiply, stimulate the immune system to produce localized pro-inflammatory hormones called cytokines. The immune system then produces an inflamed comedo inside the pilosebaceous unit.