Acne is a skin disorder affecting the hair follicles and sebaceous glands on the face, chest, and back.

Hair follicles are the tube-like structures that produce and hold the hair; the sebaceous glands attached to the hair follicles make an oily substance called "sebum," which lubricates and protects the surface of the skin.

The sebaceous gland is attached to the hair follicle by a tubular structure called a duct, which carries the gland's oily secretion into the hair follicle and then to the surface through a structure called the "pilosebaceous duct".

It is in and around the pilosebaceous duct that acne occurs.

The blemishes that make up acne take several different forms. This is in contrast to other skin conditions in which there is only one type of eruption the rash of chicken pox is made up exclusively of small blisters, for example.

Knowing the variety of blemishes that occur in acne is im-portant, since it will help you to understand the causes of acne and why some acne treatments are more helpful than others.