Yellow clay against the signs of ageing?

Skin ageing is a completely normal phenomenon: over time, the skin undergoes several structural and biochemical composition changes that alter its appearance. The main signs of ageing are as follows:

• A loss of suppleness and firmness : beyond our twenties, the production of collagen and elastin by fibroblasts decreases, leading to the loss of skin suppleness and elasticity, as well as its thinning. Frequent exposure to the sun exacerbates this phenomenon as the radicals free that this activity generates in the body cause damage to DNA, proteins, and cells, and promote skin ageing mechanisms. These are also accelerated by smoking as cigarettes themselves contain several free radicals. The loss of skin suppleness often results in the appearance of wrinkles.

• Loss of hydration : the skin tends to become drier over time. This is due to a decrease in sebum production in the sebaceous glands. Sebum is a watery/oily mixture that normally forms part of the hydrolipidic film, a protective veil on the skin's surface that limits water loss. As the skin becomes drier, it is also more prone to dehydration fine lines.

• The brown spots : they gradually form throughout life, as sun exposure is repeated. Brown spots result from an accumulation of melanin in the epidermis, the synthesis of which is triggered by UV rays. Tobacco, pollution or an unbalanced diet can also cause oxidative stress in cells, which promotes pigmented spots.

Yellow clay is often incorporated into age-targeting treatments due to its antioxidant properties. Indeed, yellow clay contains iron and copper, metals necessary for the proper functioning of superoxide dismutase enzymes (SOD). These are metalloproteins that catalyse the degradation of certain free radicals. For this, they require metallic cofactors, such as copper and iron.

Yellow clay thus helps to neutralise free radicals before they weaken the structure of the extracellular matrix. It therefore has a protective effect on collagen and elastin fibres, allowing it to delay skin sagging. Furthermore, the direct action of yellow clay on free radicals limits the formation of brown spots.

Finally, yellow clay is capable of stimulating cellular renewal. This property also helps to delay skin sagging as cellular renewal tends to slow down with age. The removal of dead cells then becomes less efficient but can be supported by the application of a treatment enriched with yellow clay.

Some properties of the copper found in yellow clay suggest that this natural ingredient also has an effect on established wrinkles and fine lines. Copper ensures the activity of lysyl oxidase, an enzyme that catalyses the formation of aldehyde from lysines. The aldehydes produced during this reaction are reactive and assemble together, which causes the cross-linking of collagen and elastin fibres. This process is essential for stabilising collagen and ensuring the integrity of elastin. This firming property of yellow clay was demonstrated in a study conducted on mice where the application of a clay poultice accelerated the synthesis of collagen fibres. Of course, caution is necessary as this study was conducted on rodents, but a similar mechanism can be assumed in humans, with an effect on wrinkles and other signs of skin sagging.

• Thèse de François HERNOT. L’argile, son utilisation à l’officine (2016).

• FRERICH B. & al. Silicon-dioxide-polyvinylpyrrolidone as a wound dressing for skin defects in a murine model. Journal of cranio-maxillo-facial surgery (2017).