What Is Polysilicone-18?
Polysilicone-18 is a man-made polymer created by linking together ethanolamine, glycidoxy-terminated PPG-7 and glycidoxypropyl-terminated dimethicone. The result is a flexible silicone-based chain that combines the smooth feel of dimethicone with the lightweight character of polypropyl glycol segments. First explored in the late 1990s as chemists searched for new ways to add softness without heavy build-up, it found a place in hair care laboratories thanks to its balanced mix of slip and breathability.
The production process starts with propylene glycol that is reacted to add epoxy (glycidoxy) groups. These reactive ends are then opened by ethanolamine and by siloxane units from dimethicone. Careful control of temperature and pH lets the small pieces join into a uniform polymer while keeping it free of harsh residues. Once purified it appears as a clear slightly viscous liquid that blends easily with water-based or silicone-based formulas.
Today Polysilicone-18 shows up most often in rinse-off and leave-in hair products. You will see it listed on the back of shampoos, conditioners, masks, serums, color-protect sprays and frizz-control creams. A few lightweight skin primers also use it to give a silky feel without clogging pores, but its main stage is still the hair aisle.
Polysilicone-18’s Cosmetic Benefits/Uses
Formulators choose Polysilicone-18 for one key job in hair care products.
As a hair conditioning agent it coats each strand with a thin flexible film that smooths the cuticle, reducing friction and making detangling easier. The film reflects light so hair looks glossier and feels softer. Because the polymer is lightweight it rinses clean without leaving a heavy residue, which helps fine or oily hair types keep their bounce.
Who Can Use Polysilicone-18
Polysilicone-18 is considered suitable for all hair and skin types, including sensitive or acne-prone skin, because it forms a breathable film that does not clog pores or trap excess oil. Those with very oily scalps might prefer lighter formulas, yet the ingredient itself is not known to aggravate sebum production.
The polymer is fully synthetic and contains no animal-derived components, so products featuring Polysilicone-18 are generally appropriate for vegans and vegetarians. Brands should still confirm their finished formula is cruelty free.
No specific warnings exist for pregnant or breastfeeding women using Polysilicone-18 topically. Current safety data show minimal absorption through skin, but this is not medical advice. Expectant or nursing mothers should discuss any new hair or skincare product with a healthcare professional to be sure it fits their individual situation.
Polysilicone-18 is not known to cause photosensitivity. It neither absorbs UV light nor makes skin or hair more vulnerable to sun damage, so it can be used morning or night without affecting sunscreen performance.
The ingredient is compatible with most other common cosmetic actives and does not interfere with hair color treatments or chemical relaxers, making it a versatile choice in mixed routines.
Potential Side Effects/Adverse Reactions
Individual responses to topical Polysilicone-18 can vary. The points below outline potential side effects that have been reported on rare occasions. When the ingredient is properly formulated most users experience none of these issues.
- Mild scalp or skin irritation such as itching or redness
- Allergic contact dermatitis in individuals already sensitive to silicones or amines
- Eye irritation if the product accidentally drips into eyes during application or rinsing
- Build-up that may leave hair feeling heavy or limp if the formula is not rinsed thoroughly, especially on very fine hair
If any adverse effect occurs, stop using the product and consult a healthcare professional or dermatologist for guidance.
Comedogenic Rating
Rating: 0 – 1 (essentially non-comedogenic)
Polysilicone-18 forms a breathable lightweight film that sits on the surface of skin without blocking pores. Its large polymer size stops it from slipping into follicular openings and the ingredient is used at relatively low levels in finished formulas. Real-world reports of breakouts linked specifically to Polysilicone-18 are extremely rare, which supports the very low rating.
Because of this profile it is generally considered suitable for people who are prone to acne or clogged pores. Only if the overall product is heavy in oils or waxes could the final formula become pore clogging.
One extra note: as with any film-forming silicone, incomplete cleansing can let residues mix with sweat and sebum over time. A thorough wash removes this risk.
Summary
Polysilicone-18 is a synthetic silicone-based polymer added to hair products to condition strands, boost shine, reduce friction and make detangling easier. It does this by laying down an invisible flexible film that smooths the cuticle yet rinses clean so hair keeps its natural movement.
While not as famous as workhorses like dimethicone, the ingredient has a steady following among formulators who want a lighter feel without sacrificing slip. You will mainly meet it in mid-range salon shampoos and leave-in sprays rather than mass-market lines.
Current safety data show low irritation potential, negligible absorption and a very low comedogenic score, making it safe for most users. As with any new cosmetic product give it a quick patch test first to be safe and enjoy the smooth results.