Acne is caused when skin cells shed too quickly in hair follicles.
This clogs the follicle, producing comedones, more commonly
known as whiteheads and blackheads. These can then become inflamed,
Acne medicines may contain ingredients that
remove the top layer of dead skin
(such as salicylic acid,
and ingredients that have antibacterial action. Some ingredients
reduce sebum production; others reduce inflammation.
Sulfur used to be quite common in acne medications, but
while it was effective at reducing inflammatory lesions, it caused
more whiteheads and blackheads, from which the inflammatory lesions
form. For this reason, it is usually combined with something like
salicylic acid, or resorcinol, to eliminate the comedones.
Resorcinol unclogs pores by causing dead skin cells to slough off.
It also has anti-fungal and anti-bacterial effects.
Benzoyl peroxide prevents the pores
from clogging up by removing dead skin cells. It also kills the
bacterium Propionibacterium acnes that causes acne. It has
anti-inflammatory effects and reduces oxygen free radicals and
fatty acids on the skin.
Salicylic acid unclogs the pores, and
reduces inflammation. It is also somewhat effective at killing
Salicylic acid is a Beta Hydroxy Acid.
Glycolic acid is an Alpha Hydroxy Acid, as are lactic acid, citric acid,
among many others. Hydroxy acids are compounds that are both
alcohols and acids at the same time. Hydroxy acids are used
as chemical peeling agents. Alpha hydroxy acids can make the
skin more sensitive to ultraviolet light by removing the protective
outer layers of the skin.
Some Alpha hydroxy acids: