Polysilicone-13

Polysilicone-13 is a silicone-based polymer—a chain of silicon atoms bonded with oxygen. It is a synthetic ingredient commonly used in hair and scalp care formulations. Unlike smaller silicone molecules, polysilicone-13 is a larger polymer that forms a protective layer rather than penetrating deeply into the hair shaft.In skincare and hair products, it functions primarily as a conditioning agent. It works by coating the outer surface of hair fibres, smoothing the cuticle layer and creating a sleeker appearance whilst also reducing friction between strands.

Polysilicone-13 deposits a thin, occlusive film on the surface of hair fibres. This polymer coating fills microscopic gaps in the cuticle layer—the overlapping outer scales of the hair shaft—creating a smoother, more uniform surface. The result is reduced friction between hairs and improved tactile feel.The conditioning benefit arises from this occlusive nature; by sealing the cuticle, the polymer helps to reduce transepidermal water loss from the hair and prevent moisture evaporation. This is particularly relevant for hair that has been damaged, chemically treated, or is naturally dry and …

Polysilicone-13 is a leave-in or rinse-off conditioning agent typically found in shampoos, conditioners, and hair serums. For best results, apply conditioners containing this ingredient to the mid-lengths and ends of hair, avoiding the scalp if your hair is fine or prone to greasiness. If using a hair serum, apply sparingly to damp hair and distribute evenly with a comb. It pairs well with moisturising ingredients and works across most hair types, though results are most noticeable on dry, curly, or textured hair.

Polysilicone-13 is generally well-tolerated and is approved for use in cosmetics in the EU, UK, and US. It is non-toxic and non-allergenic in standard cosmetic concentrations. Those with silicone sensitivity should avoid it, though true silicone allergy is rare.