Acne is a disorder of the body’s pilosebaceous units. Each unit consists of a sebaceous gland and a canal or follicle, which is lined with cells called keratinocytes and which contains a fine hair. Most numerous in the skin of the face, upper back, and chest, sebaceous glands manufacture an oily substance called sebum, which is released onto the skin’s surface through the follicle’s opening, or pore. All the constituents of the narrow follicle—the hair, sebum, and keratinocytes—may form a plug that prevents the sebum from reaching the surface of the skin through the pore. The plug allows a strain of bacterium, called Propionibacterium acnes, to multiply in the plugged follicle. As bacteria.
