Pilosebaceous follicle

Protects the skin Sebum is secreted by the sebaceous glands. It reaches the surface of the skin through the hair follicles and plays an essential role: combined with sweat it protects the skin from dehydration by creating a hydrolipid film. It also provides the skin with lipids reinforcing its barrier, maintaining hydration and suppleness.

Found all over the body and especially the face Situated in the dermis, the sebaceous glands are unevenly distributed on the surface of the entire body (except for palms of hands and soles of feet where there are none). They are bigger, larger and more numerous on the face, in particular on the forehead and the upper back. The quantity of sebum produced is therefore greater on the face than the rest of the body.

The hyper keratinization - from left to right:
follicule sébacée, micro comedo, closed comedo, open comedo

• - Excessive secretion of sebumDuring puberty in the hair follicle (hyperseborrhoea), the production of androgen hormones create excess sebum on the surface of the skin which then becomes oily. At adulthood, the sebaceous glands of imperfection-prone skins are stimulated by a greater number of nerve endings. Their sebaceous glands produce too much sebum which encourages the development of imperfections.

• - Imperfections and microcysts: clogged follicle The duct draining the sebum fills up and the pore gets clogged. The sebum is trapped resulting in the formation of a microcomedon: the imperfections or microcyst appears.

• - Bacteria proliferation The bacteria responsible for imperfections (Propionibacterium imperfections) is found very early on skin, but its true colonisation only begins 1 to 3 years before puberty. It develops around the hair follicle causing an inflammation and is found on almost all adults presenting imperfections.

• - Imperfections : from inflammation to appearance Bacteria present in the hair duct breaks down the sebum into fatty oils which irritate the skin. This causes inflammation and an infection of the microcysts and imperfections leading to the appearance of imperfections (papules, pustules, nodules).

Skin section: cellular differentiation and desquamation

Permanent cell renewal The keratinocytes make up 80% of the epidermal cells. They originate in the deepest layers of the skin and migrate to the surface in about 1 month. During their migration, they differentiate and produce keratin.

With imperfections, the natural process is disrupted. In the case of imperfections, an abnormal intensification of the keratinisation of the upper layers of the epidermis is observed. The horny cells, normally thin and loose become firm and stuck. They are no longer easily sloughed off and disrupt the natural process of desquamation (elimination of dead cells).

The increased production of sebum causes a sebum plug of non homogeneous colouring leading to the formation of comedons. It is therefore necessary to encourage cell renewal to act against these imperfections.

Innervation of the skin

The skin: a very complex sensory organ The connections between the nerves and the skin are very tight. The skin has numerous specialised sensory receivers responding to different stimuli (touch, pain, temperature, itching, mechanical stimulations). All these stimulations are picked up by the receivers and transmitted to the brain via a network of nerve fibers. The neurotransmitters are the messengers of information between the skin and the nervous system.

Sensations of discomfort Two neurotransmitters (substance P and CGRP) released by the nerve endings intensify inflammatory reactions. Sensitive skins show strong reactions to these two neurotransmitters: resulting in sensations of irritability and discomfort.