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Types of Acne

  /  Types of Acne
Understanding Acne

What type of acne do I have?

There are many categories and subtypes of acne, as well as different severity gradings for acne. In addition, certain medical conditions may have an effect on an individual's acne and response to acne treatments.

In order to successfully treat acne, it is important to first diagnose the type of acne that is responsible for the break-outs.

There is no universal classification system for acne; the extensive variety of clinical presentations makes it challenging to develop and implement such a system. As for grading of severity of acne, these are patient-specific, and depend on a number of factors. Although acne severity is generally graded into mild, moderate and severity, there is no universal way to grade acne into these categories. We generally use the Global Acne Grading System to help during consults. The clinical type of lesions, presence of scarring, presence of draining lesions or sinus tracts, lack of therapeutic response, and the psychological impact of acne are some of the features our doctors take into account when evaluating a patient.

Practically, the most useful way to classify type of acne would be to use a system of description of the actual lesions. Based on this, one of the simplest classification systems would be 2 main types: non-inflammatory (comedonal) and inflammatory.

Non-Inflammatory Acne

Non-inflammatory acne is characterized by comedones; these comedones are more commonly known as whiteheads (closed comedones) and blackheads (open comedones).

  • Whitehead / Closed Comedone
  • Blackhead / Open Comedone

Inflammatory Acne

As the non-inflammatory acne progress, they can develop into inflammatory lesions (papules, pustules, nodules and cysts) if they are not treated early.

  • Papules
  • Pustules
  • Nodules
  • Cysts
acne - blackhead

Whiteheads / Closed Comedones

If a clogged pore of sebum and dead skin cells is closed and covered by a thin layer of skin, it is known as a closed comedone, or commonly, a whitehead. The sebum and dead skin cells accumulate, resulting in a thick substance that forms a skin-coloured “plug” under the skin. If these become infected by the P. acnes bacteria, they can turn into inflammatory acne.

Blackheads / Open Comedones

If a clogged pore of sebum and dead skin cells remains open on the surface of the skin, the sebum inside the pore oxides upon contact with air; this oxidation causes a dark colouration that can appear black, brown or grey, resulting in a “blackhead”. Similar to closed comedones, open comedones can become infected and turn into inflammatory acne.


Strictly speaking, papules are small (<1cm diameter), solid skin elevations with no visible fluid or pus within. In acne, they are often erythematous (red) and tender (painful to touch) due to inflammation, and may be surrounded by oedema (swollen and inflamed tissue). Papules don’t display a visible pore and are usually the first type of inflammatory acne to affect the skin.


Pustules are small circumscribed raised lesions that contain pus, which may be white to yellow. The main difference between a pustule and papule is that a pustule contains pus – which is made up of white blood cells, dead skin cells and dead bacteria, as a result of the body’s inflammatory process in its attempt to clear the acne. Similar to a papule, the skin surrounding a pustule tends to be red and inflamed.

nodular acne example
cystic acne example


Nodules are larger (>1cm), raised, solid lesions. They are located deeper than papules and pustules, primarily in the dermis and/or subcutaneous tissue (below the dermis). Most of the nodule may well be “hidden” below the skin surface, such that it is more often palpated (felt) under the skin rather than seen. Similarly to papules, nodules form from a build-up of bacteria, skin cells, and sebum in the follicles, but this formation is rooted deeper in the skin. Nodules can be very painful.

Nodules can remain under the skin for a long time. They may be dormant and then suddenly “flare up” again. If squeezed or ruptured, these nodules can spread over a larger area of the skin and cause deep infections. These can then cause damage to the skin and lead to the formation of scars.


Cysts are similar to nodules, except for the presence of pus within them. They may appear as a large, fluctuant (swollen), and red lumps on the skin. They may occur independently, or may merge and be “linked” through sinus tracts.

Other subtypes of acne

Acne Tarda / Adult / Hormonal Acne

Acne tarda (adult acne) is defined as acne that develops (late-onset acne) or continues (persistent acne) after 25 years of age. It is thought to be associated with hormones and fluctuations in hormone levels. Other important influencing factors include a genetic predisposition, smoking, inappropriate skincare and make-up and stress.

The clinical features of acne tarda are quite specific: inflammatory acne in the lower facial region (also known as the U-zone) or macrocomedones (microcysts) spread over the face. In men with acne tarda, involvement of the trunk is common.

Acne Cosmetica

Cosmetic products that contain comedogenic ingredients can induce the formation of acne lesions. Irritant reactions to cosmetic products can also produce eruptions that resemble acne. Acne cosmetica can occur anywhere on the body but is most common on the face, neck, hairline, and scalp. Heavy, oil-based hair products may contribute to the development of acne on the forehead (where it is then termed pomade acne).

People typically experience cosmetic-induced acne on the chin and cheeks more than than on the forehead. It commonly presents as small, whitish bumps, although these can also develop into inflammatory acne lesions.

Cosmetic-induced acne tends to be stubborn, sometimes lasting for years as the person using makeup enters into a vicious cycle of covering the breakouts, which lead to further breakouts. Cosmetic-induced acne can take months to form which can lead to confusion as a breakout seems to come out of nowhere, when in fact, cosmetics slowly caused the acne to form over time.

Acne Mechanica

Clothing and parts of clothing (such as turtlenecks, bra straps and shoulder pads), orthopaedic casts, and sports helmets may all cause acne mechanica, in which occlusion of pilosebaceous follicles leads to comedone formation.

In addition, soaps and detergents remove sebum from the skin surface but do not alter sebum production. Repetitive mechanical trauma caused by scrubbing with these agents may worsen the disorder by rupturing comedos, promoting the development of inflammatory lesions. Thus, patients with acne should refrain from rubbing their faces, picking at their skin or excessive exfoliation.

Acne Fulminians

Acne fulminians is a very rare but severe form of painful, inflammatory nodulocystic acne with scarring. The patient may feel ill and be systemically unwell, in addition to having skin features. A form of drug-induced acne fulminians is associated with the use of isotretinoin.

Other conditions that may be confused with acne

There are a few other conditions that may seem like acne, but they’re not – and sometimes, they may appear along with acne and get self diagnosed, and not receive the appropriate treatment for both.


Milia are commonly seen as small, skin-coloured or whitish, firm bumps on the surface of the skin, usually about 1-2mm in diameter. They are composed of keratin, a naturally-occurring protein found in the skin. They can arise from the pilosebaceous unit or sweat ducts. Milia usually develop spontaneously, but may also be found more often after a healing process or at a site of frequent friction or trauma.


Folliculitis refers to inflammation of the superficial or deep portion of the hair follicle. Folliculitis can present with papules, nodules, redness, swelling and pain; this may be confused with inflammatory acne. However, it is important to make the differentiation between the two conditions as the bacteria involved in folliculitis is different from that for acne and hence treatment options are different.


Rosacea is a complex condition with various contributing factors, including some degree of immune system dysregulation causing inflammation, ultraviolet (UV) radiation such as sunlight, vascular (blood vessels) hyper-reactivity (hence the red and “flushed” appearance common in rosacea) and certain micro-organisms on the skin surface (which are different from the P. acnes bacteria). It is also common to have papules and pustules in rosacea, hence some people with rosacea might mistakenly think they have acne instead.