Sebum is a substance secreted by the sebaceous gland on the surface of our skin and is essential for its proper functioning.
Summary
The epidermis is protected by a film called the hydrolipidic film which covers the entire surface of the skin and is composed of sebum, water and sweat.
Sebum plays several crucial roles(1):
Sebum is produced by the sebaceous gland. This gland is always attached to a pilous follicle, more commonly known as a hair. This follicle emerges on the surface of the skin to discharge the sebum produced.
The sebaceous gland is responsible for regulating sebum secretion.
The sebaceous glands are present all over the body except on the palms and soles of the feet, and are more numerous in certain areas (the face (especially on the T-zone), scalp, chest, back). These are known as oily areas.
Sebum is a lipidic substance of yellowish color. Its texture is oily.
It constitutes a veritable ecosystem and enables the multiplication of a resident commensal flora (microorganisms naturally present on the surface of the skin and mucous membranes).
These microorganisms are saprophytes, i.e. they live on our skin without being pathogenic or harmful to our organism. They include bacteria, such as staphylococci, and yeasts such as those of the Malassezia genus.
Excess sebum is one of the causes of seborrheic dermatitis. In larger quantities in the so-called "oily" areas, it constitutes a favorable environment for the development of Malassezia-type yeasts, naturally present on the surface of the skin.
This yeast, when present in high proportions, can, in addition to or influenced by other factors, trigger a specific inflammatory reaction. This results in redness and accelerated renewal of scalp and skin cells, causing white or yellowish scales on the surface of the skin: this is a flare-up of seborrheic dermatitis.
There is therefore a genuine link between the development of seborrheic dermatitis and sebum.
(1) Dermato-info.fr, French dermatology society
