Puberty and adolescence are almost universally recognized as of primary importance in the etiology of acne vulgaris. Other factors which are often blamed, such as constipation, irrational diet, malnutrition, etc., are just as likely to occur at any other period in life. Many cases outlast adolescence, and a small proportion begin later in life, but these are more likely to be of the rosacea type.
Without exactly saying so, many authorities have acquiesced in the idea that acne vulgaris is of endocrine origin. The bacteria usually found are simply secondary invaders which have taken advantage of a favorable soil consisting of excessive oil or comedones. It has never been definitely determined whether comedones result from excessive activity or defective activity of the sebaceous glands. In either event, it would appear that the endocrine system, gonads, thyroid, etc., coming into increased activity during adolescence in some way affect the sebaceous glands.