There are many myths about the causes of acne, many of which are not true. But all doctors agree that acne is a hormonal disease and in our article on hormones and acne you can find more information on this topic.

We also know that some people have a greater genetic propensity for blemishes, and that certain medications, tobacco, stress, and inadequate skin care can worsen acne. There is also evidence of a correlation between diet and acne-prone skin. You can find out more about the possible causes and triggers of acne.

This article focuses on the physiological causes of acne, on what actually happens on our skin. We examine the multiple and complex factors involved in the appearance of blackheads, pimples and pimples, and how they transform into acne. You can find more information about the different types of acne here.

It all starts with invisible microcomedones on the skin

A comedone is a clogged hair follicle. “Microcomedón” is the name given to a microscopic, subclinical comedon (still invisible). Microcomedones are formed as the cells that synthesize keratin multiply in the skin. This process occurs naturally, without problems, in healthy skin, while the microcomedones dissolve. But, in people with acne, the dissolution process is accompanied by inflammatory reactions known as microinflammations.

Microinflammation: the root cause of the acne cycle

Acne is primarily an inflammatory disease. According to the latest research, microinflammation is one of the main causes of acne . It is believed to be the result of the body’s immune system reacting to bacteria, lipids, and androgens (male sex hormones). *

* “We know there is inflammation in all stages of acne development, not just when blemishes are already visible on the surface of the skin ” . Indicates Dr. Markus Reinholz, dermatologist

Seborrhea and hyperkeratosis follow

Internal factors such as hormonal changes (for example, during adolescence and during the monthly cycle) and medications, and external factors such as environmental influences, can lead to increased production of both sebum (what is known as seborrhea) such as corneocytes (known as hyperkeratosis), causing blackheads, blackheads, and pimples. All of these factors also play a role in the growth of bacteria, ultimately leading to acne-associated papules and pustules.  More information about the terms used to describe acne, such as papules and pustules, and what they mean can be found in the section titled  Blem-prone skin in general .


The sebaceous glands secrete an oily substance called sebum, which keeps the skin and hair supple and soft. People with blemish-prone skin tend to have higher levels of androgens (male hormones) in their blood. Your sebaceous glands may also be more sensitive to androgens. These androgens promote the growth of the sebaceous glands and the excessive production of sebum. This excessive sebum production is called seborrhea.

Excess sebum on the surface of the skin interferes with the natural processes by which the skin detaches from the cells (known as flaking). The composition of the sebum lipids that accumulate in the sebaceous glands also triggers inflammation.



Hyperkeratosis is the abnormal thickening of the outer layers of the skin. It is caused by excessive production of skin cells (also called corneocytes) in the ducts of the sebaceous glands and by inadequate peeling (exfoliation) of the dead cells as excess sebum sticks them to the surface. These cells form plugs that block the sebaceous glands.

The Propionibacterium acnes (or P. acnes) bacterium, which normally lives on the surface of the skin without causing problems, also plays its role in hyperkeratosis. It creates a biofilm (thin layer) on the skin’s surface, which disrupts the normal peeling process and contributes to the formation of plugs.

Blackheads, pimples and pimples form

The sebum accumulates in the blocked sebaceous glands and the follicle wall thickens, causing comedones (blackheads and blackheads), and also pimples:


A swollen blemish (somewhat elevated above the surface) that fills with pus and is usually painful. “Grain” is a collective name, which is often used to describe all imperfections: comedones, papules, and pustules.

Diagram of a black point

A small, dark, flat spot on the skin. The dark coloration is caused by oxidation of the sebum by oxygen and has nothing to do with dirt.

A round imperfection that rises somewhat above the surface, with a milky white covering and a type of grain.

Bacterial growth exacerbates visible inflammation, leading to acne.

The accumulation of sebum secreted by the sebaceous glands represents an ideal environment for the growth of bacteria, particularly P. acnes. It begins by colonizing the duct of the sebaceous glands and causes the sebum to break down. This breakdown produces substances that increase inflammation and results in papules and pustules that are associated with acne.

In severe cases, the follicular wall explodes in the late stages of inflammation. Lipids, fatty acids, corneocytes (cells), bacteria, and cell fragments are released, which can lead to increased inflammation in the surrounding skin.

You can check one or more of the different forms that acne takes in the section entitled “The different types of acne” and also the influence that it can have on your skin in the sections related to acne and hyperpigmentation and acne and scars.