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What is Acne?

Updated: Mar 14, 2021

So many of us struggle with acne, and we all want a quick-fix which will give us clear and beautiful skin overnight. I hear you. But, before starting to use all these expensive cosmetics on your face, it's important to understand what acne actually is, what it is caused by, and all the different types of acne.

So, let's get into is cysters!

What is acne?

"Acne is a chronic inflammatory disease of the pilosebaceous unit resulting from androgen-induced increased sebum production, altered keratinisation, inflammation, and bacterial colonisation of hair follicles on the face, neck, chest, and back by Propionibacterium acnes." (1)

This means that acne is a condition caused by increased sebum (oil) production, changes in skin cell turn-over, inflammation, and increased levels of bacteria. Acne forms when the hair follicle is blocked, and these is a build up of matter which is trapped in pores.

Acne is still largely a mystery in the medical field due to its different causes. Each case varies from patient to patient, therefore, it is very hard to pin-point a specific treatment suitable for all.

Who is affected by acne?

Many people can be affected by acne, yet by far the largest group of people to experience this skin condition are adolescents (2).

79% to 95% of adolescents will be affected by acne.

40% to 54% of adults over the age of 25.

12% of middle-aged women and 3% of middle-aged me.

People who are susceptible to oily skin and have had family history of acne, are more likley to suffer from this skin condition.

How is acne formed?

Acne is formed when there is a fault in the process of sebum production.

Pores are 'little holes' in the skin which are made up of a hair follicle and a sebaceous gland. If you look closely, you may be able to see them on your face.

Sebaceous glands release sebum (oil) to moisturise the hair follicle and the stratum corneum (very top layer of the skin).

When this mechanism works properly, the sebum is spread out over the skin and it remains healthy and nourished. (3)

Acne is when this mechanism goes wrong.

The pores can become clogged, which leads to a build up of matter in the pore - creating what we know as: acne.

What can clog the pores?

- Excess sebum.

- Bacteria (p. acnes).

- Dead skin cells.

- Thickened inner lining of hair follicles.

- Dirt/excess product.

Causes of acne.

Changes in endocrine system.

Androgens (e.g., testosterone) are hormones which stimulate the production of sebum in the sebaceous glands. The influx of this oily substance may cause the pores on the face, back and chest to not drain properly, leading to the pore becoming blocked and swells (4).

This is why we observe acne in adolescents as this is when hormonal changes are the most drastic; during puberty. Young men are likely to experience a chronic effects of acne as their testosterone levels rise and stay high. Young women may experience periods of larger outbreaks 14 days before their period, as that's when androgenic levels are at their highest (5).

Women undergoing menopause may also experience acne due to the changes in testosterone and oestrogen levels (4).

Changes to the skin microbiome.

Each one of us has a unique microbiome, and it's very important for our skin health. The commensal bacteria Propionibacterium acnes plays a key role in acne. Studies show, that there is no significant differences in numbers of p.acnes on patients with acne skin and patients with healthy skin, however, patients suffering with acne had different strains of the bacteria, which could lead to the development of acne (6).

The skin microbiome can be affected by a wide variety of factors including: early life exposure, the environment, cosmetics, and anti-microbial agents (7).

Hyperkeratinisation (retention hyperkeratosis).

Retention hyperkeratosis is a phenomenon where corneocytes become cohesive, preventing them from shedding normally. This creates a slight thickening of the skin, which can clog pores, creating a build up of sebum under the skin (8).

Increased exposure to impurities.

Being exposed to dust, dirt, pollution and comedogenic (pore-blocking) products, increases your chances of developing acne. These fine particles can get into the pores which blocks them, and builds up sebum in the pore.

What are the types of acne?

There are six different types of acne.

Inflammatory acne: (9)


Small red bumps found just underneath the surface of the skin, without a defined centre. These spots are hard, raised and tender with slightly swollen, red skin surrounding it.

What you think of when we say spots.


Pustules have a defined centre and tend to be slightly larger. The centre contains a white-yellow puss filled with immune-system cells and bacteria.

Similar to papules, but have a white tip containing pus, look a little like inflamed whiteheads.


Large hard lumps, usually painful and inflamed, deep underneath the skin. Nodules form when the clogged pores damage surrounding tissue. They can create acne scars.

What we think of when we say acne.


Large pus-filled soft lumps, found in the deeper layers of the skin, even deeper than nodules - and can cause severe scaring.

These carry the greatest risk of scaring, which needs to be treated.

Non-inflammatory acne: (10)

Blackheads (open comedones)

Open pores filled with sebum and dead skin cells that have become oxidised, giving it a black appearance.

Small black or yellow bumps.

Typically found on the nose.

White heads:

Very similar to blackheads, filled with sebum and dead skin cells, however, they are not open, instead, there is a thin layer of skin covering it.

They are firmer than black heads and will not empty when squeezed.

Acne myths

"The more I wash my skin, the less acne I will have"

This is not strictly true, as most of the reasons for acne come from within the skin, not on it.

"I just need to change my diet"

It's always good to invest in a good diet, yet there are no studies which show a direct correlation between acne and diet.

"The sun clears acne"

There is no evidence for this, in fact, excess sun exposure can be damaging if you're using acne treatments which sensitise the skin.

To see how you can effectively treat acne, click here.


1. Williams, H., Dellavalle, R. and Garner, S., 2012. Acne vulgaris. The Lancet, 379(9813), pp.361-372.

2. Cordain, L., Lindeberg, S., Hurtado, M., Hill, K., Eaton, S. and Brand-Miller, J., 2002. Acne Vulgaris. Archives of Dermatology, 138(12).

3. NHS, 2021. Acne - Causes. [online] Available at: [Accessed 13 March 2021].

4. Healthline, 2021. Hormonal Acne: Why It Happens and How to Treat It. [online] Healthline. Available at: [Accessed 13 March 2021].

5. Reed BG, Carr BR. The Normal Menstrual Cycle and the Control of Ovulation.

6. Fitz-Gibbon, S., Tomida, S., Chiu, B., Nguyen, L., Du, C., Liu, M., Elashoff, D., Erfe, M., Loncaric, A., Kim, J., Modlin, R., Miller, J., Sodergren, E., Craft, N., Weinstock, G. and Li, H., 2013. Propionibacterium acnes Strain Populations in the Human Skin Microbiome Associated with Acne. Journal of Investigative Dermatology, 133(9), pp.2152-2160.

7. Moskovicz, V., Gross, A. and Mizrahi, B., 2020. Extrinsic Factors Shaping the Skin Microbiome. Microorganisms, 8(7), p.1023.

8. Anina Lambrechts, I., Nuno de Canha, M. and Lall, N., 2018. Exploiting Medicinal Plants as Possible Treatments for Acne Vulgaris. Medicinal Plants for Holistic Health and Well-Being, pp.117-143.

9. Huizen, J., 2018. Acne types in pictures: Explanations and treatments. [online] Available at: [Accessed 13 March 2021].

10. Healthline, 2021. Types of Acne: Pictures, Treatments, and More. [online] Healthline. Available at: [Accessed 13 March 2021].

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