A versatile, water-soluble silicone wax that delivers the characteristic silky texture of silicones without the greasy residue or potential for buildup. It acts as an effective skin conditioner, humectant, and foam booster, making it a staple in clear, aqueous formulations like serums and toners.
- INCI Name:
- Bis-PEG-18 Methyl Ether Dimethyl Silane
- Chemical/Scientific Name:
- Siloxanes and Silicones, di-Me, 3-hydroxypropyl Me, ethers with polyethylene glycol Me ether
- Common Aliases:
- Water-Soluble Silicone, PEG-18 Methyl Ether Dimethyl Silane, Silwax WS
| Category: | Moisturizers |
| Source Origin: | Synthetic |
| Comedogenic Rating: | 0 |
| Primary Industries: | Skincare, Haircare, Personal Care |
| Solubility: | Water |
At a Glance: Properties & Effects
| Hydration/Moisture: | |
| Texture Enhancement: | |
| Soothing/Calming: | |
| Irritation Risk: |
Primary Benefits:
- Reduces the tackiness and stickiness of high-Glycerin formulations.
- Provides a “silky” and “velvety” skin feel without the occlusion of traditional oils.
- Functions as a humectant by binding Aqua to the upper layers of the stratum corneum.
- Enhances the spreadability of sunscreens and heavy creams.
Potential Risks:
- Negligible risk of irritation; generally considered safe for sensitive skin.
- Possibility of mild eye irritation if used at very high concentrations in rinse-off products.
Biological Action & Cosmetic Profile
Hybrid molecular structures define this ingredient’s unique performance in cosmetic chemistry. It consists of a hydrophobic dimethyl silane core grafted with hydrophilic polyethylene glycol (PEG) chains. This specific architecture allows it to remain completely soluble in Aqua while retaining the lubricity and slip characteristic of a silicone like Dimethicone. Unlike standard silicones, it does not require emulsification to stay stable in water-based systems, enabling the creation of clear, lightweight gels and serums.
Surface tension reduction is another critical function of this molecule. By lowering the surface tension of a formula, it helps the product spread more evenly across the skin’s topographical peaks and valleys. When added to formulas containing high concentrations of Butylene Glycol or other polyols, it effectively masks the heavy or “syrupy” feel that often deters consumers. This makes it an essential tool for formulators seeking to balance high hydration with a sophisticated, dry-touch finish.
Moisturization occurs through humectancy rather than pure occlusion. The PEG chains contain oxygen atoms that form hydrogen bonds with water molecules, slowing down trans-epidermal water loss (TEWL) without creating a thick, plastic-like film. This makes it particularly suitable for oily or acne-prone skin types that require hydration without the risk of pore-clogging associated with heavier waxes or oils.
Broader Applications & Origins
Manufacturing this ingredient involves the hydrosilylation of methyl-capped polyethylene glycol ethers. While purely synthetic, its role in modern “water-gel” technology is indispensable. In addition to leave-on skincare, it is frequently found in shaving gels and hair conditioners, where it improves wet combing and reduces the stripping sensation of surfactants. Its low melting point (near skin temperature) ensures that it melts instantly upon contact, providing immediate sensorial feedback.
Routine Integration
Synergies:
- Glycerin: Neutralizes the sticky after-feel of this potent humectant.
- Sodium Hyaluronate: Enhances the gliding sensation during application.
- Panthenol: Works alongside pro-vitamin B5 to improve skin softness and barrier suppleness.
- Alcohol Denat: Softens the drying sensation of alcohol-heavy formulas, such as toners or sunscreens.
Conflicts:
- No known chemical conflicts; compatible with most active substances and preservatives.
Clinical Consensus & Safety
Dermatological evaluations by the Cosmetic Ingredient Review (CIR) Expert Panel have repeatedly affirmed the safety of this ingredient. In their 2015 assessment, the panel concluded that it is safe for use in cosmetics in the present practices of use and concentration, which typically range from 1% to 15%. Because it is a large polymer, it does not easily penetrate the skin barrier, further reducing the potential for systemic toxicity or deep-tissue irritation. It is non-comedogenic and is not considered a sensitizer in human repeat insult patch tests (HRIPT).
Is Bis-PEG-18 Methyl Ether Dimethyl Silane a “bad” silicone?
No. In cosmetic chemistry, “bad” silicones are often perceived as those that cause buildup or clog pores. Because this version is water-soluble, it easily washes off and does not accumulate on the skin or hair, making it a preferred choice for clean-feeling formulations.
Can this ingredient cause acne?
Scientific data indicates a comedogenic rating of 0. It does not possess the greasy or occlusive properties of traditional oils, meaning it is unlikely to contribute to the formation of comedones or breakouts.
Why is it used in “oil-free” products?
It is chemically classified as a silicone wax, not an oil. Since it is water-soluble, it allows brands to achieve a smooth, “silky” texture without using actual vegetable or mineral oils, maintaining the “oil-free” claim for marketing purposes.