Acne vulgaris (or common acne)
Is an extremely common disorder among young people - the average teenager is considered to be very lucky if acne is not part of his or her adolescent troubles.
Acne arises specifically as a result of an obstruction to the outlet of the sebaceous glands. Sebum collects at the opening of the gland and chemical changes(specifically, oxidation) produce blackheads - known medically as comedones. This exacerbates the obstruction, impairing the normal flow of sebum onto the surface of the skin.
The blocked sebaceous gland swells, with sebum collecting in the ducts of the gland. Infection sets in and produces an inflammatory reaction. If the contents of the gland and subsequent infection seep into the surrounding tissue, a more extensive inflammatory reaction may take place.