Were we to discuss the cause of acne a hundred years ago, it would be quite simple. Louis Duhring,Pathfinder for American Dermatology, considered the etiologies of acne. They “are numerous and are very different in their nature…. The most frequent and ordinary origin of acne is puberty…. [the] general disability of the system occupies a conspicuous place. Under this head may be grouped all those abnormal conditions arising from imperfect physical development, improper nutrition, and other defects of the economy, whether organic or functional.” So much for the 19th