The cause of acne is really not known. The process by which a pimple develops is highly intricate. While we do know that a pore collapses on itself and blocks sebum (oil) from escaping, we do not fully understand why this process takes place in one sebaceous gland versus another.
Adult acne and teen acne may be caused by hormones, diet, evolutionary biology, vitamin deficiency, stress, and more. Probably all or some of these factors are involved.
