Acne usually starts shortly after puberty due to hormonal changes and increased oil secretion. However, it is common to see patients (particularly women) in their 30s, 40s, and 50s with adult onset acne. Internal hormonal changes may play a role.
Acne develops when hair follicles, the site of acne, get plugged with dead skin cells. Then, sebum (oil) and bacteria accumulate and lead to inflammation. Acne is not caused by dirt; it is caused by a combination of genetic and hormonal factors. The diagrams below will help you to understand the different types and stages of acne.
Normal Hair Follicle
This is a pore, also called a follicle. Each pore has sebaceous glands and most have a hair in them.
Sebaceous glands naturally produce oil, called sebum, which keeps your hair healthy and flexible. Normally sebum and dead skin cells released into the follicle drain to the surface of your skin as it is produced.
Acne occurs when the pore is blocked, causing a build up of sebum and dead skin cells. This soup of dead skin cells and sebum creates an environment for bacteria to grow and they begin to flourish inside of the follicle. This early stage of acne is called a microcomedone. Microcomedones occur under the skin and are small enough that the human eye cannot see them.
A whitehead occurs when the pore remains closed. Whiteheads can be so small the human eye cannot see them.
A blackhead occurs when the pore is open. The sebum, bacteria, and dead skin reach the surface and the oxygen turns the mixture a dark brown or black color.
Two things can occur to comedones.
- The follicle slowly releases its contents to the surface, draining the build up of sebum, dead skin, and bacteria, and returning to normal, or:
- The follicle wall ruptures. If the follicle wall ruptures, the skin surface becomes red and swells. This is called inflammation.
In self-defense, the body sends white blood cells through the ruptured follicular wall to kill off the infection inside. The combination of inflammation and white blood cells create a papule.
While fighting the infection, white blood cells die and create pus. As the pus reaches the skin surface a pustule is formed, also called a pimple or zit.
The entire follicle can collapse if the rupture is on the bottom of the follicular wall. This creates a nodule. Nodules are hard to the touch, more painful than other lesion types, and deep red or purple in color.
Sometimes a severe inflammatory reaction can result in very large pus filled lesions, which are called cysts. Because it affects deeper layers of the skin, cystic acne frequently causes scarring.