Battling bacteria

The microcomedo may develop into, and remain, a comedo. But
sometimes it becomes an inflammatory lesion. Inflammation is a
reaction of the skin to disease or injury; in the case of acne, the
inflammation is a reaction to the bacteria known as Propioni-
bacterium acnes. Signs of an inflammatory lesion include swelling,
redness, heat, and sometimes pain. The presence of these bacteria
does not mean that poor hygiene is a cause of your acne.
Here’s a list of common inflammatory acne lesions:
 Papule: A small, firm red bump, commonly referred to as a
pimple or zit. It’s made up of inflammatory blood cells and
doesn’t contain obvious pus.
 Pustule: A papule that contains pus, a whitish, goopy sub-
stance that’s really just a bunch of white blood cells. Pustules
are also known as “pus pimples.”
 Nodule: A large and often tender, lumpy, inflamed, pus-filled
papule or pustule that’s lodged more deeply in the skin. The
term cyst is often used interchangeably to mean “nodule”
because of the resemblance of a nodular acne lesion to a cyst.
One other common acne lesion is sometimes formed late in the life
cycle of a lesion from the remains of an inflammatory lesion:
 Macule: A macule is a flat red, purple, or brown spot that
forms where a papule or pustule used to be. A macule remains
for a while after an acne lesion has healed or is in the process
of healing. For more details on how your skin heals, check out
Chapter 16.
To see what the preceding lesions look like, take a look at the color
section of this book.
P. acnes jumps in
In order for comedones to move up the inflammation chain into a
full-blown lesion, they need the help of a certain bacteria. You
know how people add yeast to make a cake rise? Well, the bac-
terium known as Propionibacterium acnes helps make the zits rise.
From now on, I just call him (or is it her?) P. acnes, for short.
P. acnes is an anaerobe. That means that it prefers to live in areas
that have very little oxygen such as in the low oxygen environment
that exists in a hair follicle.
P. acnes generally minds its own business. These usually “friendly”
and harmless bacteria are present on everybody’s skin, but in the
proper environment (like a nice roomy, oily, hair follicle), they can
cause trouble: In some kids and adults who are predisposed to
have acne, P. acnes invade the plugged hair follicles (the come-
dones) and multiply.
These P. acnes never become bored or go hungry because they
continuously munch on the oily, fatty sebum that serves as a food
supply for them. They accomplish this culinary feat by producing
chemicals known as enzymes. Enzymes are proteins that cause a
chemical change in other substances without being changed them-
selves. P. acnes enzymes are like our knives and forks that help us
to chop up our food into smaller pieces so that it’s digestible.