Carboxymethyl Chitosan

Carboxymethyl chitosan (CMCS) is a modified form of chitosan, a naturally-derived polymer sourced from crustacean shells. The carboxymethyl modification makes it water-soluble and better suited to skincare formulations, where it functions as a film-former and thickening agent.In skincare products, it creates a lightweight protective layer on the skin surface and helps control the viscosity (thickness) of formulations. It also has gel-forming properties, which allows it to be used in hydrogel-based products.

Carboxymethyl chitosan works primarily through physical rather than biochemical mechanisms. When applied to skin, it forms a thin, flexible film that sits on the surface. This film helps reduce transepidermal water loss (TEWL), keeping moisture in the skin for longer.Because it is a polymer, it also increases product viscosity, making formulations easier to apply evenly. In hydrogel systems, it can absorb and hold water within its three-dimensional network structure, maintaining a hydrating environment against the skin.

Carboxymethyl chitosan is typically used as a supporting ingredient rather than an active, so look for it listed in the INCI (ingredients) towards the middle or later sections. It works well in hydrogel masks, lightweight moisturisers, and serums. No special application technique is needed; use as you would any other skincare product of that type.

Carboxymethyl chitosan is generally well-tolerated and is approved for use in cosmetics in most markets. Those with shellfish sensitivities may wish to check formulation details, though allergic reactions are rare.