Silk is made of two different types of proteins: fibroin and sericin. Fibroin is the filaments of silk itself and makes up to 80% of the silk by weight, while sericin is the "glue" that binds the filaments together and makes up the remaining 20%.
All proteins are made up of amino acids. Silk has 18 of the 20 amino acids that are found in the human body. 80% is made up of three: alanine, glycine and serine.
The silk fibroin - which gives silk its strength - mimics the body's "natural moisturising factor" (NMF), which improves hydration and reduces "trans-epidermal water loss" (TEWL). Together, this protects the skin from the effects of pollution and scoops up free radicals thanks to antioxidant properties.
The sericin has a number of hydrating and remedial properties, which can help wound-healing and even anti-ageing.
Alanine is found mostly in fibroin and is a conditioning and hydrating agent that helps reduce TEWL thanks to the fact that it is small enough to penetrate the skin barrier.
Glycine is also found in fibroin and is known to improve signs of ageing by increasing water retention and stimulating the production of collagen.
Serine is found in sericin and has significant moisturising benefits, which is why it is often found in hair care products in addition to skincare.In conclusion, silk not only has great benefits, but its retaining properties let the other active ingredients do a great job too!