What it is
Methyl Methacrylate Crosspolymer is a synthetic acrylic polymer composed of porous, spherical microbeads. The tiny spheres absorb excess sebum to give a mattified finish and impart a smooth, silky slip to products. When light strikes them it scatters in many directions, the soft-focus effect, which visually softens the look of fine lines and blurs the perimeter of pores while staying transparent on skin rather than appearing cakey. It is also classed as a film former and viscosity-increasing agent and appears often in sun care and primers.
Safety & warnings
Because these polymer microspheres have a high molecular weight, they are too large to penetrate the skin barrier and remain on the stratum corneum where they perform their oil-absorbing function, which is associated with a low likelihood of irritation or sensitization for most users. The Cosmetic Ingredient Review Expert Panel has assessed methyl methacrylate crosspolymer together with related PMMA polymers and concluded they are safe for use in cosmetics, drawing in part on prior FDA safety data for PMMA in medical devices.
Origin & sourcing
It is fully synthetic, made by polymerizing methyl methacrylate into a crosslinked network. In CosIng it is described as 2-propenoic acid, 2-methyl-, 1,2-ethanediyl ester, polymer with methyl 2-methyl-2-propenoate, with CAS number 25777-71-3, and it is closely related to the broader polymethyl methacrylate (PMMA) family of polymers.
Questions everyone asks
What is the soft-focus effect?
The microspheres scatter light in many directions, which visually softens the appearance of fine lines and blurs the edges of pores while staying transparent on the skin.
Does it absorb oil?
Yes. The porous spheres absorb excess sebum, helping give a smoother, more mattified finish, which is why it is common in sun care and primers.
Is it the same as PMMA?
It belongs to the same polymethyl methacrylate family; the crosspolymer version is a crosslinked network of acrylic microspheres assessed alongside PMMA by the CIR Expert Panel.