Acne affects nearly 100% of the population at some point. For
some, acne is mild and transient; for others, it can be severe
and long lasting. Scarring from severe acne can be permanent and
disfiguring (see section on Acne Scars). Acne usually begins
around the time of puberty. Acne may improve after puberty, but
for many, acne persists into and during middle age. Acne lesions
form when the opening of oil glands (called sebaceous glands) in
the skin become blocked. Trapped oil builds up within the gland,
causing inflammation. The swelling within the oil gland can
become so intense that the oil gland (and associated hair
follicle) can rupture, leading to further inflammation. While
the surge of hormones during puberty likely triggers this
process, other factors such as stress, diet, and the influence
of other hormones may also play a role. A bacterium called
Propionibacterium acnes that is normally present on the skin
likely plays a role in acne, but the precise link is still
unclear. Any person with moderate