No known benefits

Polymethylsilsesquioxane at a glance

  • Used as a film former and skin conditioning ingredient
  • Is a powder with round-shaped particles
  • Is used in amounts up to 55.2% in cosmetics
  • Deemed safe as used in cosmetics, with no evidence of toxicity or sensitisation

Polymethylsilsesquioxane description

Polymethylsilsesquioxane is a polymer formed from the condensation and hydrolysis of the silicone methyltrimethoxysilane. In cosmetics, it functions primarily as a film former and skin conditioning ingredient. In its raw form, it is a powder with round particles. In a survey of cosmetic formulations, polymethylsilsesquioxane was found to be used in amounts as high as 55.2%, but most often at concentrations of 4.9% or less. The independent Cosmetic Ingredient Review panel found that polymethylsequioxane is safe as used in cosmetics, with no evidence of toxicity or sensitisation. This silicone polymer is also not known to clog pores.

Polymethylsilsesquioxane references

  • https://thedermreview.com/polymethylsilsesquioxane/
  • https://www.cir-safety.org/sites/default/files/polysilsesquioxanes.pdf
  • Archives of Toxicology, 2012, pages 1641-1646
  • Journal of Society of Cosmetic Chemists, 1993, pages 488-493

Peer-reviewed, substantiated scientific research is used to assess ingredients in this dictionary. Regulations regarding constraints, permitted concentration levels and availability vary by country and region.

Ingredient ratings


Proven and supported by independent studies. Outstanding active ingredient for most skin types or concerns.


Necessary to improve a formula's texture, stability, or penetration.


Generally non-irritating but may have aesthetic, stability, or other issues that limit its usefulness.


There is a likelihood of irritation. Risk increases when combined with other problematic ingredients.


May cause irritation, inflammation, dryness, etc. May offer benefit in some capability but overall, proven to do more harm than good.


We couldn't find this in our ingredient dictionary. We log all missing ingredients and make continuous updates.

Not Rated