When closed comedones burst, their contents get into surrounding
tissues. In response, the immune system sends more blood to
the area, which causes inflammation to begin or worsen. As a result,
the closed comedone and the area surrounding it become red
and swollen. This redness and swelling appears on the skin in the
form of a papule.
Papules are small, firm, red bumps. They are only mildly inflamed
because they form before pus has reached the area. Therefore,
papules are more severe acne lesions than comedones, but
milder than acne lesions that contain pus. However, because
papules are inflamed, they are often tender to the touch.
As the inflammation worsens, the immune system sends pus to
the area. When this happens, pustules form. Because pustules are
caused by severe inflammation, they often feel hot and may be
quite sensitive to the touch. Not surprisingly, pustules are larger than papules. They are often
about the size of the tip of a person’s little finger. Pustules are
red at the base, with a yellowish, pus-filled inner region. Aman who
had pustules on his face, shoulders, and neck recalls: “They were
big old welts filled with white poison and surrounded by red rings.”
Although a pustule’s red base forms on the surface of the skin,
the pus-filled core is near, but still underneath, the skin. However,
as inflammation worsens and more pus is formed in the area, the
pus-filled core of a pustule begins to swell like a balloon. When
this happens, it is not uncommon for pustules to pop open and
spill pus onto the skin. Aman recalls: “In the morning before I went
to school, I’d have big welts on my shoulders and neck. Sometimes
at school they would break without me even knowing. When I got
home I’d have stains on my shirt.”
Cysts
Just as worsening inflammation causes a pustule to expand upward
through the skin’s surface, worsening inflammation also
causes pustules to expand downward. When this occurs, a cyst is formed. Cysts are packed with large amounts of pus that extend
deep below the skin’s surface. Due to swelling, cysts may be several
centimeters in diameter. Most cysts are red or purple and extremely
painful. Since cysts form when inflammation and infection
are the most severe, cysts are the most serious type of acne lesions.
