This article discusses the physiological mechanisms underlying mild to moderate acne. As acne is a chronic medical condition, the advice of a healthcare professional remains essential for an accurate diagnosis and appropriate management.
Acne is a complex, multifactorial skin condition. Often mistakenly perceived as a simple, temporary inflammatory skin reaction, its origins are in fact much deeper. Whether it appears during adolescence or in adulthood, and is sometimes exacerbated after the summer and exposure to the sun, the mechanism leading to the appearance of an acne spot involves interconnected biological, hormonal and environmental factors. As a result, understanding the real causes of this condition affecting the pilosebaceous system is the essential first step. It is also a necessary step towards adopting an effective and long-term skincare strategy.
How do stress and hormones contribute to the development of an acne spot?
Among the main causes of this skin condition, stress and hormonal fluctuations play a major role. Stress, a common phenomenon in our modern society, plays a key role. In stressful situations, the human body reacts by increasing its production of cortisol, commonly known as the stress hormone. This excess cortisol has a direct detrimental effect on the skin’s sebaceous glands by causing excessive stimulation. In response, these glands produce an abnormal amount of sebum. This creates an environment conducive to the development of an acne spot.
At the same time, hormonal fluctuations are a key factor, particularly during adolescence, pregnancy, or the menstrual cycle. These variations involve, in particular, androgens (male hormones present in both men and women). Consequently, they lead to excessive sebum production. This hormonal instability explains why skin flare-ups can occur in successive waves throughout one’s life.
What role do the sebaceous glands play in the formation of an acne spot?
To understand exactly how an acne spot forms, we need to examine the anatomy of the skin. The skin consists of three distinct layers: the epidermis, the dermis and the hypodermis. It is within the dermis that we find the sensory nerves, sweat glands and sebaceous glands. The natural function of these glands is to produce sebum, an oily substance whose primary purpose is to waterproof the skin, maintain its moisture levels and protect it from external microbial attacks.
Acne develops when the pilosebaceous system (which comprises the hair follicle, the hair shaft and the sebaceous gland at the root of the hair) becomes chronically disrupted. This disruption involves two major abnormalities:
- Hyperseborrhoea: excessive and continuous sebum production.
- Dyskeratinisation: an abnormality in skin cell renewal that blocks the excretory duct.
The sebum then becomes trapped and stored within the skin’s pores. This closed, lipid-rich environment becomes the ideal breeding ground for the proliferation of a specific anaerobic bacterium found in the skin flora: Cutibacterium acnes (formerly known as Propionibacterium acnes). When the pore eventually ruptures beneath the skin under the pressure of this bacterial build-up, the body triggers an immediate immune response. It is this localised inflammation that manifests on the surface as a visible and sometimes painful cyst or spot.
What other everyday factors can make an acne spot worse?
Beyond hormones and stress, other internal and external factors play an active role in the appearance or severity of an acne spot. Moreover, genetic factors largely determine the sensitivity of our sebaceous glands to hormones. Diet also plays a major role. Indeed, excessive consumption of dairy products or foods with a high glycaemic index causes insulin spikes that can stimulate sebum production.
Environmental factors should not be overlooked. Air pollution and high humidity can clog the skin’s surface. Furthermore, the use of unsuitable or comedogenic cosmetics (which physically block the pores) exacerbates the problem. Finally, the sun has a paradoxical effect: whilst it may seem to dry out blemishes at first, UV rays actually cause the skin to thicken. Consequently, a few weeks after returning from holiday, the blocked pores clear. This causes the well-known ‘rebound effect’ and a proliferation of blemishes.
The development of an acne spot is never a matter of chance. It is the result of a precise biological cascade involving a combination of excess sebum, blocked pores and bacterial inflammation. All of this is influenced by our lifestyle and hormones. Treating this condition therefore requires a holistic approach that goes beyond simply exfoliating the surface of the skin.
Find out how to adapt your diet with our Article 2: Anti-acne diet and essential nutrients
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Scientific sources and medical references:
- French Society of Dermatology (SFD) – Good practice recommendations for the management of mild to moderate acne.
- French National Authority for Health (HAS) – Guidance on the appropriate use of care and treatments for juvenile and adult polymorphic acne.
- PubMed – Clinical studies on the role of cortisol (stress) and hormones in acne.
- Vidal – Pathophysiology of acne vulgaris and mechanisms of follicular dyskeratinisation.
FAQ – What are your frequently asked questions about the causes of acne?
Why does stress actually cause spots?
When you are stressed, your neuroendocrine system releases cortisol. This hormone increases the activity of the sebaceous glands. The skin then produces more sebum, which clogs the pores and creates the ideal anaerobic environment for the bacterial proliferation responsible for inflammation.
What is the difference between Propionibacterium acnes and Cutibacterium acnes?
They are exactly the same bacterium. Scientific taxonomic classifications have evolved to rename Propionibacterium acnes as Cutibacterium acnes (or C. acnes), in order to better reflect its specific place within the human skin microbiome.
Is acne genetic?
Yes, partly. Genetics determine the size of your sebaceous glands, their baseline sebum production levels, and the sensitivity of your hormone receptors to androgens. Consequently, if both your parents suffered from severe acne, your risk of developing it is statistically higher.
