We SKIN2KIM use vegan ultra low molecular collagen (Hydrolysed Vegetable Protein) which is smaller than 500 Dalton to maximise absorption and deliver visible results for smoother, healthier-looking skin.
‘According to studies from 2000, molecules larger than 500 Daltons cannot penetrate the skin’s corneal layer, which explains why allergens, topical drugs, and transdermal treatments are typically smaller than this size.’

Source: The 500 Dalton rule for the skin penetration of chemical compounds and drugs, J D BosM M Meinardi