Polybutylene Terephthalate

Polybutylene terephthalate (PBT) is a synthetic polyester — a polymer created from chemical synthesis rather than derived from natural sources. It belongs to the same family of materials used in textiles and packaging, and in skincare it functions primarily as a film-forming agent and viscosity controller.In formulations, PBT creates a thin, continuous layer on the skin surface and helps regulate the thickness and flow properties of products. It appears in approximately 0.1% of skincare products, making it a relatively uncommon but not experimental ingredient.

Polybutylene terephthalate works by depositing as a thin, continuous film when a product is applied and the solvent evaporates. This film sits on the skin surface, forming a physical barrier that can help minimise moisture loss.It also functions as a viscosity modifier, meaning it adjusts how thick or thin a formulation is, which affects how the product spreads and feels on application. This dual role — both barrier-forming and texture-controlling — makes it useful in a range of skincare formats.

Polybutylene terephthalate is a leave-on ingredient, typically found in serums, moisturisers, and primers. As with any film-forming agent, it works best when applied to clean skin and allowed to dry fully before application of additional products. If you find it leaves a heavy or occlusive feel, layering with lighter textures or using it selectively (for instance, on areas that need extra smoothing) may help optimise comfort.

Polybutylene terephthalate is generally recognised as safe in cosmetic use and is well-tolerated by most skin types. No common sensitivities or adverse effects are widely reported, though as with any ingredient, individual tolerance may vary.