What causes the appearance of pimples?

Whether it's open or closed comedones, papules or pustules, the formation of pimples is often closely linked to the pilosebaceous follicles, the skin appendages where hair originates. These hair follicles are attached to a sebaceous gland, responsible for the production of sebum. Pilosebaceous follicles are primarily found in areas prone to acne, such as the forehead, nose, cheeks, chin, chest, and back. The formation of pimples involves several biological processes, sometimes working in synergy.

• An increase in sebum production: The primary factor responsible for the emergence of blemishes is hyperseborrhea, which is an excessive production of sebum by the sebaceous glands. Indeed, although it is not always the case, individuals prone to skin imperfections often have a combination or oily skin. This overactivity of the sebaceous glands causes an accumulation of sebum in the hair follicle, leading to its blockage and the dilation of the skin's pores. In response to this blockage, a plug forms and a blemish appears.

• An accumulation of dead cells: The obstruction of hair follicles can also be caused or exacerbated by a dysfunction in the renewal of keratinocytes, the cells of the epidermis. When the latter is altered, dead cells accumulate on the skin's surface and can mix with sebum. This phenomenon can contribute to clogging pores and forming pimples.

• Bacterial colonization: Lastly, the proliferation of Cutibacterium acnes, a bacterium naturally present on the skin, can exacerbate the appearance of blemishes. By feeding on the triglycerides in sebum, this microorganism releases free fatty acids that irritate the follicular walls and trigger an inflammatory response. This excessive presence of C. acnes is often correlated with the formation of inflammatory blemishes such as papules or pustules.

The mechanisms of pimple formation, as previously discussed, do not activate on their own but stem from various causes, which are decoded below.

• Heredity.

  We are not all created equal when it comes to blemishes, and some people are naturally more prone to them than others. Individual genetic predispositions significantly influence the occurrence of skin imperfections by playing a crucial role in the regulation of sebum production. Indeed, some individuals inherit genes that increase the activity of the sebaceous glands or enhance sensitivity to androgen hormones, stimulating sebum production. These familial predispositions manifest as a higher likelihood of pore blockage, one of the key factors in the formation of blemishes. Genetics also influence the skin microbiome and the individual immune response. This can particularly result in more or less pronounced inflammations in response to free fatty acids generated by the bacterium C. acnes.

  Several studies have explored the existing link between genetics and acne. One of them, conducted in 2006 with 151 patients, showed that 54% of them had a family history of acne. Although this difference is small, the authors deemed it significant. This hypothesis of a genetic component in acne was further confirmed in 2014 during another study. This study involved 221 patients and revealed a family history of acne in 70.1% of them. A familial component thus appears to play a role in the formation of acne lesions.

• Hormonal changes.

  Another common cause of pimples: hormonal fluctuations. Indeed, an excess of androgen hormones in the blood, mainly testosterone and dihydroxytestosterone (DHT), stimulates the activity of the sebaceous glands, thereby creating a skin imbalance conducive to the development of C. acnes. This is particularly what happens during adolescence, where the amount of hormones secreted increases significantly, often leading to acne problems. However, puberty is not the only period of life prone to hormonal changes and pimples, which can appear later. In adults, hormonal pimples predominantly affect women, due to the many hormonal variations they encounter throughout their lives (menstrual cycle, pregnancy, menopause, contraceptive pill...).

• Stress.

  Stress plays a fundamental role in hormone balance, and therefore in the amplification and frequency of acne breakouts. Indeed, during periods of stress, cortisol is secreted in large quantities. This hormone has an impact on the skin by stimulating the adrenal glands, which are responsible for the production of androgen hormones that in turn regulate sebum production by the sebaceous glands. A study conducted in 2017 at a medical school involving 144 female students examined the link between acne and stress and found a correlation between these students' stress levels, measured on a scale from 0 to 30, and the severity of their acne. The numerical summary of this study is presented in the table below. However, the results should be interpreted with caution as it is possible that the stress experienced by the participants may be partly due to their acne, and not the other way around.

• Diet.

  Diet also plays a role in the occurrence of pimples. More specifically, foods with a high glycemic index, such as white bread, processed products, or fruit juices, are strongly suspected of exacerbating acne. Indeed, when a food with a high glycemic index is consumed, the concentration of glucose in the blood significantly increases. In response, the pancreas stimulates the secretion of insulin, which in turn promotes the release of the growth factor IGF-1. This factor increases the levels of androgens in the blood, thereby intensifying sebum production and the risk of blemishes. It is also interesting to note that meat and dairy products, despite their low glycemic index, possess powerful insulin-stimulating properties. They are also likely to play a role in the formation of pimples.

• Some cosmetic products.

  Finally, in some cases, blemishes can be caused by certain cosmetic products. This is then referred to as cosmetic acne. Most often, this type of skin imperfection takes the form of small bumps on the skin or closed comedones. Products that can cause cosmetic acne are referred to as comedogenic. They are generally very occlusive and can clog the skin's pores. The concept of comedogenicity is particularly important for people with combination to oily skin as they are often prone to cosmetic acne. It should be noted that each person reacts differently: the same product can be non-comedogenic for one individual and cause blemishes for another.

Note : Contrary to a fairly widespread misconception, pimples are not a sign of poor hygiene.

No matter what the cause of your pimples is, if they make you feel self-conscious, it's important to seek advice from a dermatologist so they can guide you towards a treatment suitable for your situation.

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