2. Excessive production of skin oils
Acne is, in essence, an accumulation of oils that gather beneath the surface of your skin. Your skin is not a flat surface, it might look like that especially if you have smooth skin, but under a microscope or another powerful lens you will quickly realize that it has countless little holes. These are the points at where the sebaceous channels open to the air. These channels connect your sebaceous glands, which produce your skin oil.
Skin oil is meant to protect your skin and keep it smooth and hydrated and combat the effects of drying when exposed to certain environmental hazards. Naturally, your sebaceous glands will produce oil and let it leak out through the sebaceous channels. If for some reasons they make too much oil, it accumulates beneath your skin and cause the pimples and other skin features commonly associated with acne.