The "-" indicates a reduction in the ability of the sebaceous glands to produce sufficient sebum (sebaceous hyposecretion), as well as a discrepancy in the synthesis of natural moisturising factors by keratinocytes, which give the skin the ability to retain water. Tightness, irritation, dehydration fine lines, redness, flaking, dull complexion... are characteristic of this skin type.
Indeed, this lack of lipids reduces the effectiveness of the hydrolipidic film. The skin then becomes vulnerable to all forms of aggression (UV rays, pollution, bacteria, etc.), triggering inflammatory responses, and no longer effectively prevents transepidermal water evaporation. Moreover, this alteration in the barrier function leads to a dysregulation of Langerhans cells (cells of the immune system), which begin to induce disproportionate inflammatory responses when they are overly stimulated.
Several factors can influence this low sebum secretion, leading to these disturbances: frequent washing, certain medicinal treatments, unsuitable skincare, seasonal variations, tobacco, UV radiation, genetics... However, although this skin type is more prone to wrinkle formation due to its lack of suppleness, it is, on the other hand, less susceptible to skin sagging given that its thinner epidermis suffers less from the effects of gravitational pull.