What are the benefits of collagen for the skin?

Collagen is the most abundant protein in the human body, accounting for nearly one-quarter of its total protein content.

Synthesized by fibroblasts, it constitutes the framework of connective tissues, notably the skin, bones, tendons, and ligaments, and provides them with mechanical strength and flexibility. Among the 28 collagen types identified, type I is the most abundant in the dermis, where it makes up about 80 to 90% of total collagen. Its triple-helix structure, rich in glycine, proline, and hydroxyproline, enables it to assemble into strong fibers—a property essential for skin cohesion.

With age, the production of collagen declines gradually, and the fibers become stiffer and more fragmented. Starting at age 25, a loss of about 1% per year is observed. This decline, exacerbated by UV radiation, smoking, pollution, and glycation—a process that stiffens fibers due to glucose—is partly responsible for the appearance of wrinkles on the skin, as well as the loss of its firmness.

The collagen has become an extremely popular active ingredient in cosmetics, particularly in treatments aimed at slowing skin aging. This popularity is driven by a clear goal: to compensate for the progressive decline of collagen in the skin with age, a phenomenon that contributes to the loss of firmness, elasticity, and the appearance of wrinkles. Incorporated into numerous serums, creams, and masks, topical collagen is presented as an ally for strengthening skin structure and improving skin hydration.

• Collagen exhibits antioxidant properties.

  Topical collagen first exhibits significant antioxidant activity that helps limit certain mechanisms involved in skin aging. By neutralizing a portion of the free radicals generated by UV exposure, pollution, or specific endogenous metabolic reactions, it contributes to reducing the cellular damage responsible for dermal fiber degradation and the loss of skin firmness.

  Several studies in vitro have shown that peptides derived from collagen can act as free radical scavengers. A study conducted on hydrolyzed collagen sourced from sheep skin demonstrated that the more the collagen was hydrolyzed, the greater its antioxidant activity. The ABTS and DPPH assays — two benchmark methods for assessing a compound’s ability to stabilize free radicals — showed maximum activity after four hours of hydrolysis, reaching 67.6% neutralization for ABTS and 52.75% for DPPH.

The study also underscores that lowering the molecular weight of peptides is critical: the shorter the collagen fragments, the higher their antioxidant capacity. When used daily, this form of collagen thus constitutes an attractive support for preventing skin aging.

• Collagen exhibits hydrating properties.

  The moisturizing properties of collagen applied to the skin are due to several complementary mechanisms. First, this active ingredient forms a thin film on the surface of the epidermis that limits transepidermal water loss and protects the skin from external aggressors. Moreover, thanks to its structure rich in hydrophilic amino acids, it attracts and retains water molecules in the superficial layers, thus helping to maintain an optimal hydration level in the stratum corneum. Finally, collagen helps improve adhesion between epidermal cells, a process essential to the integrity of the skin barrier : the more cohesive the cell-to-cell junctions, the more effectively the skin retains water.

  The interest in topical collagen application and its effect on hydration has been evaluated in various studies, including one conducted with individuals having a sensitive and atopic skin. In this randomized, double-blind, placebo-controlled trial, 40 women with this skin type applied for four weeks a formulation containing a gluco-oligosaccharide and a collagen tripeptide or the same cream without these actives. Several skin parameters were measured before and after use, including hydration level and transepidermal water loss. The results showed significantly greater improvements in the group receiving the active formulation compared to the placebo.

• Collagen is believed to have restructuring effects.

  Topical collagen is often described as a restructuring active ingredient—meaning it can support the skin’s extracellular matrix. This matrix, composed primarily of collagen, elastin, and glycoproteins such as versican, provides mechanical strength, cohesion, and tissue elasticity. As noted earlier, with advancing age and repeated environmental insults, fibroblast activity declines, and the protein fibers that form the extracellular matrix become stiffer, fragment, and lose their organized structure. Nevertheless, collagen peptides are believed to have the ability to stimulate these dermal cells, thus promoting skin regeneration and maintaining tissue structure.

  To better understand this restructuring potential, a study in vitro evaluated the effect of collagen peptides on human dermal fibroblasts. In this study, fibroblasts were exposed to 0.01% collagen peptides for 24 hours, and researchers measured the expression of three extracellular matrix genes: COL1A1, encoding type I collagen, ELN, encoding elastin, and VCAN, encoding versican. The results show a marked stimulation of fibroblast activity.

It is important to note, however, that native collagen is a fibrous protein with a high molecular weight (300 kDa) that prevents it from crossing the epidermal barrier. Therefore, to be properly absorbed, it must be hydrolyzed into collagen peptides with a molecular weight between 2,000 and 6,000 Da.

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