Understanding Acne: How Skin, Hormones, and Microorganisms Work Together

What is acne

Acne originates within the hair follicle, also known as the pilosebaceous unit. This unit consists of a hair shaft, a sebaceous gland, and the canal that opens onto the skin's surface. The sebaceous gland produces sebum, a natural oily substance that protects and softens the skin. In acne-prone skin, these processes become disrupted, allowing a combination of sebum, dead skin cells, and bacteria to accumulate inside the pore.

Scientific literature describes acne as a complex, multifactorial condition. There is no single root cause; rather, various biological and environmental factors contribute to its development. The primary drivers include increased sebum production, abnormal keratinization within the pore, changes in sebum composition, the activity of specific bacteria, and localized inflammatory responses in the skin.

To approach acne from a practical perspective, read our articles on what you can do about acne and skincare habits to avoid. These articles translate the underlying theory into daily skincare practices.

How acne develops step-by-step

Dermatological publications typically highlight four core processes that collectively contribute to the development of acne:

1. Increased sebum production
   Primarily driven by hormones, the sebaceous glands can produce excess sebum. This leads to an accumulation of natural lipids inside the pore.
2. Abnormal keratinization in the follicle
   The skin constantly renews itself. In acne-prone skin, keratinocytes (dead skin cells) within the hair follicle clump together more rapidly and fail to shed evenly. This process is known as hyperkeratinization.
3. Formation of comedones
   The combination of excess sebum and clumped skin cells causes a partial or complete blockage of the pore. This manifests as open comedones (blackheads) and closed comedones (whiteheads).
4. Bacterial overgrowth and inflammation
   The bacterium Cutibacterium acnes is a normal resident of the skin microbiome. However, in a blocked follicle rich in sebum and lacking oxygen, this bacterium can multiply rapidly. This triggers localized inflammatory responses, resulting in red bumps, papules, pustules, and sometimes deep-seated nodules.
   
   

The role of sebum and its composition

Sebum is a complex mixture of triglycerides, wax esters, squalene, free fatty acids, and small amounts of cholesterol and antioxidants. While the quantity of sebum is important, its chemical composition also plays a major role in acne development.

Since sebum production is a key factor, understanding your specific skin type can be highly beneficial. For more information, read our articles on what oily skin actually is or how combination skin behaves.

Studies show that the ratio between different fatty acids and the rate of lipid oxidation can heavily influence the skin. For instance, a relatively low level of linoleic acid in sebum is associated with a higher tendency for pores to clog. Additionally, oxidized squalene can activate inflammatory pathways in the skin, which can exacerbate existing blemishes.

Sebum acts simultaneously as a protective shield and as a contributing factor to breakouts. The goal, therefore, is not to strip the skin of sebum entirely, but rather to understand and restore the balance between its production, composition, and flow.

Abnormal keratinization within the pore

The outermost layer of the skin consists of keratinized (dead) cells that function like bricks, held together by mortar-like lipids. This shedding and renewal process is called keratinization, and it occurs both on the skin's surface and within the hair follicle.

In acne-prone skin, the keratinocytes inside the follicle canal change in both number and behavior. They accumulate more rapidly and fail to shed evenly. This increases the likelihood of sebum and dead skin cells forming a plug that blocks the pore. This process often begins in the early stages, long before any blemishes become visible on the surface.

The skin microbiome and bacteria

The skin is home to a vast community of microorganisms, including bacteria, yeasts, and viruses, collectively known as the skin microbiome. In a healthy state, a natural balance exists between these various species.

The bacterium Cutibacterium acnes plays a central role in acne. However, it is not merely its presence that causes issues, but rather the diversity of its strains and how they interact with other microorganisms and your body's immune system. Indeed, certain strains of Cutibacterium acnes are far more closely associated with driving inflammation than others.

Acne is therefore not a simple bacterial infection, but the result of a disrupted interaction between sebum, keratinization, the microbiome, and localized immune responses.

The immune system and inflammatory processes

Inflammation is a fundamental driver of acne. The immune system reacts to triggers inside the hair follicle, such as bacterial byproducts, oxidized lipids, and damaged skin cells. This prompts the release of inflammatory mediators like cytokines and chemokines.

Research shows that inflammatory processes are often present in the very early stages of acne, sometimes even before visible comedones (blackheads) develop. This highlights that acne is not merely a mechanical issue of clogged pores, but a process in which the immune system is actively involved.

The intensity and duration of these responses vary from person to person and are partly influenced by genetic factors. This explains why some individuals primarily experience blackheads, while others develop inflamed papules and pustules.

Hormones and genetic predisposition

Hormones are a well-documented factor in acne. They stimulate the growth and activity of the sebaceous glands. During puberty, hormonal surges drive up sebum production. In adults, hormonal fluctuations—such as those associated with the menstrual cycle—can also trigger breakouts.

Genetic predisposition determines how sensitively your sebaceous glands respond to hormonal signals and how keratinization unfolds inside the hair follicle. If acne runs in your family, you are naturally more likely to experience it to some degree.

Lifestyle and environmental factors

Alongside biological drivers, lifestyle and environmental factors can influence the severity of acne. These elements can either exacerbate or soothe your skin's natural predisposition.

The following aspects are frequently cited in scientific literature:

• Stress
  Stress hormones can increase sebum production and trigger inflammatory responses in the skin.
• Heat and high humidity
  These conditions can promote sweat accumulation and occlusion, making pores more prone to clogging.
• Cosmetics and clothing
  Heavy products or synthetic clothing fabrics that restrict airflow can trap oils and contribute to clogged pores.
• Diet
  There is no simple, universal dietary blueprint that works for everyone. Some studies suggest that high-glycemic diets or certain dairy products are associated with increased acne in some individuals, but personal responses vary widely.
  
  

In addition to lifestyle, your daily skincare routine plays a vital role. A simple, gentle routine can effectively support your skin barrier. To learn how to implement this in practice, read our guide on creating an acne-prone skin routine step-by-step.

Different forms of acne

Dermatology distinguishes between several clinical presentations of acne. These forms can occur simultaneously or at different stages in life.

• Acne comedonica
  Characterized primarily by blackheads and whiteheads, with relatively little active inflammation.
• Acne papulopustulosa
  Characterized by visible red bumps (papules) and pus-filled pimples (pustules).
• Acne nodulocystica or conglobata
  Severe forms involving deep-seated inflammation, painful nodules, and cysts, which carry a higher risk of permanent scarring.

The overall severity of acne is determined by the number and type of lesions, the duration of the flare-up, the depth of the inflammation, and the presence of scarring.

Common misconceptions about acne

• Acne is not caused by poor hygiene
  Over-washing or using harsh, aggressive cleansers will compromise your skin barrier and drive up overall sensitivity.
• Acne is not a simple bacterial infection
  Cutibacterium acnes is a normal resident of healthy skin. The complex interaction between bacteria, sebum, keratinization, and immune response is what determines whether acne develops.
• Acne is not merely a cosmetic issue
  Even though the blemishes appear on the surface, acne is a complex biological condition that can also have a profound emotional and psychological impact.
• Diet alone does not explain acne
  While diet can certainly be a contributing factor for some, acne is never determined by eating habits alone.
  
  

What this means for daily skincare

While the biology of acne is undeniably complex, daily skincare does not have to be. In practice, a gentle, highly consistent routine is far more effective than an aggressive, constantly changing regimen.

• gentle cleansing that respects and preserves the skin barrier
• limiting the overall number of products in your routine
• supporting barrier health and recovery
• avoiding aggressive formulas and physical irritants

By minimizing daily disruptions, your sebum production, keratinization, and inflammatory processes have a much better opportunity to stabilize. Discover more practical tips in our articles on what you can do about acne and our guide on which gentle botanical ingredients support blemished skin.

When to seek medical advice

Because acne can be a chronic and sometimes highly persistent condition, we recommend consulting a doctor or dermatologist in the following situations:

• If you experience painful nodules or deep-seated inflammation
• If you notice visible scarring or tissue changes
• If acne significantly impacts your self-esteem, mental well-being, or daily life
• If consistent, gentle self-care and routine adjustments yield no noticeable improvement

A medical professional can accurately assess your skin and determine which clinical treatments are best suited for your specific case.

At More Natural, we do not view acne as something to 'battle' with aggressive products. Instead, we see it as a skin condition that thrives on understanding, rest, and nurturing support of its natural functions. In practice, minimizing irritation and maintaining consistency is far more effective than complex, harsh routines.

Further reading and scientific sources

If you would like to explore the scientific literature surrounding acne in more detail, the following public resources and clinical overviews are excellent starting points:

• Acne overview on PubMed PubMed search results for acne vulgaris
• Patient information and background by the American Academy of Dermatology American Academy of Dermatology acne resource center
• Dutch general practitioner guidelines on acne NHG standard for acne
• Patient information from an academic hospital Radboudumc acne information portal

These resources are provided to deepen your understanding of the development and progression of acne. They are not a substitute for personalized medical advice.