What Is Polymethyl/Octyl/Phenyl/Propylsilsesquioxane Dimethicone Crosspolymer?
Polymethyl/Octyl/Phenyl/Propylsilsesquioxane Dimethicone Crosspolymer is a specialty silicone made by linking together several smaller silicone units, namely dimethyldimethoxysilane, propyltrimethoxysilane, octyltrimethoxysilane, methyltrimethoxysilane and phenyltrimethoxysilane. When these units react, they form a three-dimensional network that feels soft and flexible on the skin. Like most cosmetic silicones, the original building blocks come from silica, the same mineral found in sand and quartz.
Silicone chemistry began appearing in beauty products in the 1950s when formulators noticed how well these materials spread and protected the skin. Crosslinked versions such as this one are newer. They rose to popularity in the past two decades as brands looked for smoother, longer-lasting textures without the heavy feel of oils or waxes.
The manufacturing process involves controlled hydrolysis and condensation of the five different silane monomers. By adjusting temperature, pH and reaction time, chemists create a uniform gel-like matrix that traps lightweight oils or water, giving the finished polymer its signature silky glide.
You will most often find Polymethyl/Octyl/Phenyl/Propylsilsesquioxane Dimethicone Crosspolymer in primers, liquid and powder foundations, color-correcting creams, blurring balms, anti-aging serums, moisturizers, sunscreens and long-wear eye or lip products. It is also used in wash-off masks to boost spreadability and leave a smooth after-feel.
Polymethyl/Octyl/Phenyl/Propylsilsesquioxane Dimethicone Crosspolymer’s Cosmetic Benefits/Uses
This versatile silicone supports both the feel and performance of many beauty formulas.
- Film forming – Creates an even, flexible layer on the skin that helps pigments stay put, improves water resistance and gives a soft focus finish that can blur fine lines and pores
- Skin conditioning – Leaves a smooth, non-greasy surface that reduces roughness, makes skin feel silky and enhances the glide of other ingredients during application
Who Can Use Polymethyl/Octyl/Phenyl/Propylsilsesquioxane Dimethicone Crosspolymer
This silicone mesh is considered gentle enough for nearly all skin types including dry, normal, combination and oily skin. Its lightweight feel means it will not add extra oil to already shiny complexions while its smoothing property can help dry or flaky areas feel softer. People with very acne-prone or highly congested skin should note that any film former has a small chance of trapping oil and debris against the skin, though this particular polymer is classified as low risk for breakouts.
The ingredient is entirely synthetic and derived from mineral silica rather than animal sources making it suitable for both vegans and vegetarians.
No studies point to harmful effects for those who are pregnant or breastfeeding however this is not medical advice. Anyone expecting or nursing should show the full product ingredient list to their healthcare provider before use to be on the safe side.
Polymethyl/Octyl/Phenyl/Propylsilsesquioxane Dimethicone Crosspolymer does not make skin more sensitive to sunlight so it is not considered photosensitising. It is also fragrance free and non-reactive with common actives like retinol or vitamin C which lets it fit easily into most routines.
Potential Side Effects/Adverse Reactions
Reactions to topical Polymethyl/Octyl/Phenyl/Propylsilsesquioxane Dimethicone Crosspolymer vary from person to person. The following list covers potential issues that could occur even though they are unlikely for the average user when the ingredient is formulated correctly.
- Mild irritation or redness in individuals with extremely sensitive skin
- Temporary clogged pores or small comedones in those very prone to congestion especially if the product is not removed thoroughly
- Product pilling when layered over heavy creams or under certain makeup formulas which can cause small flakes to roll off the skin
- Allergic contact dermatitis a rare immune response presenting as itch or rash
If any of these effects occur discontinue use and consult a healthcare professional.
Comedogenic Rating
Rating: 1 / 5
This silicone crosspolymer sits on the skin as a breathable, flexible mesh that does not melt into pores or add extra oil. Its large, cross-linked structure makes it less likely to block follicles compared with heavier oils or waxes, which is why it earns a low score of 1. Most users, even those with combination or oily skin, tolerate it well without new breakouts.
Suitable for acne-prone and congestion-prone skin, though very sensitive or severely clogged complexions may still prefer to limit any film formers if they notice issues.
Keep in mind overall formula matters. If the product also contains rich butters or strong fragrances, those other ingredients could raise the risk of clogged pores regardless of this polymer’s low rating.
Summary
Polymethyl/Octyl/Phenyl/Propylsilsesquioxane Dimethicone Crosspolymer is a lightweight film former and skin conditioner that smooths texture, blurs fine lines and helps makeup stay put by laying down a soft, flexible layer. Its three-dimensional silicone network does the heavy lifting, giving products a silky glide without greasy residue while locking pigments and actives in place.
It pops up most often in modern primers, long-wear foundations and hybrid skincare-makeup launches. While not as famous as simpler silicones like dimethicone, it is gaining traction with formulators looking for next-gen textures that feel cloud-light yet perform all day.
Current safety data shows a very low risk of irritation, sensitization or systemic harm when used as directed. Still, every skin is different so patch test any new product that features this ingredient to make sure it plays nicely with your unique complexion.