In the course of reading about acne and other skin diseases, you’ll encounter various medical terms that may be confusing.  To help you better understand your acne and how it is categorized, we have compiled a list of common medical terms to assist you during your reading.  You can find these terms on our Acne Definitions page.

Non-Inflammatory Acne

Did you know that there are four basic types of non-inflamed acne breakouts?  When various debris clogs your pores, a comedo or blemish can form.  There is often no redness or swelling with the non-inflamed comedones.  However, if invaded by bacteria, it could turn into a pimple.

1. A microcomedo is the very beginning of an acne lesion and can occur when the sebaceous duct and pore opening becomes blocked by excess sebum and dead skin cells.  Every blemish begins as a microcomedo and can possibly turn into another form of acne.
2. Soft Closed Comedones can develop when cellular debris and sebum (oil) get trapped within the pore opening.  The pore is then covered by a layer of more dead skin cells.  The lesion remains soft.
3. A Whitehead occurs when the trapped sebum and bacteria stay below the skin surface.  Whiteheads may be so small that they are invisible to the naked eye, or they may show up as little white spots on your skin.
4. A Blackhead occurs when the pore opens up to the surface.  The sebum leaks out and turns a brown or black color because it contains the skin pigment melanin.  Blackheads tend to last a long time due to the slow drainage of the sebum to the skin surface.

Whitehead (Closed Comedo)

Blackhead (Open Comedo)

NOTE: Neither blackheads nor whiteheads should be squeezed or picked open, unless extracted by a dermatologist under sterile conditions. Tissue injured by squeezing or picking can become infected by staphylococci, streptococci and other skin bacteria.

Inflamed Acne Blemishes

When bacteria infects a comedone, or if it gets irritated by a person squeezing, inflammation occurs and often causes redness, swelling and pain.

There are four main types of inflamed acne blemishes.  These are the more inflamed form of pus -filled or reddish bumps, even boil-like tender swellings.

1. A Papule is a small, solid lesion that is slightly elevated above the skin surface.  It contains no pus or whitehead.
2. A Pustule is a typical pimple that is a dome-shaped, fragile lesion that contains pus and typically contains a mixture of white blood cells, dead skin and bacteria.  They can range in size from small to fairly large.  A pustule that forms over a sebaceous follicle usually has a hair in the center.  Acne pustules that heal without progressing into a cyst usually leave no scars.
3. A Nodule, like a papule, is solid, dome-shaped or an irregularly-shaped lesion.  They feel like a hard , painful lump under the skin.  Unlike the papule, the nodule is characterized by inflammation and can extend into deeper layers of the skin.  This can sometimes cause tissue destruction and can result in scarring.
4. A Cysts is a sac-like lesion that contains liquid or semi-liquid material such as white blood cells, dead cells, and bacteria.  Cysts are larger than a pustule and can become severely inflamed.  They also extend deeper into the skin, may be painful, and can result in scarring.  They are the most severe form of pimple.  Cysts and nodules can often occur together and form a severe form of acne called Nodulocystic.

Papule

Pustule

NOTE: See your dermatologist if you have numerous pustules, if they are highly inflamed, or difficult to control.