PEG-18 is a multifunctional synthetic polymer that acts as a potent humectant and solvent to improve product spreadability and skin hydration. It facilitates the efficient delivery of active ingredients while ensuring a lightweight, non-greasy finish in complex cosmetic formulations.
- INCI Name:
- PEG-18
- Chemical/Scientific Name:
- Polyethylene Glycol 900
- Common Aliases:
- Polyoxyethylene (18), Polyethylene Glycol (18) units
| Category: | Solvents |
| Source Origin: | Synthetic |
| Comedogenic Rating: | 0 |
| Primary Industries: | Skincare, Haircare, Topical Pharmaceuticals |
| Solubility: | Water |
At a Glance: Properties & Effects
| Hydration/Moisture | |
| Texture Enhancement | |
| Penetration Enhancement | |
| Irritation Risk |
- Primary Benefits: Increases skin water retention, improves formula glide, and stabilizes volatile active substances.
- Potential Risks: Minimal; rare hypersensitivity in extremely reactive skin.
Biological Action & Cosmetic Profile
Polyethylene glycols like PEG-18 are produced through the polymerization of ethylene oxide. This specific molecular weight variant contains an average of 18 oxyethylene units, creating a structure that is highly hygroscopic. When applied topically, the polymer creates a network of hydrogen bonds with Aqua molecules. This interaction locks moisture into the upper layers of the epidermis, providing immediate relief for dehydrated skin without the occlusive weight of traditional oils or butters.The molecule functions as a strategic delivery vehicle within a formula. By slightly modifying the lipid bilayer structure of the stratum corneum in a reversible manner, PEG-18 assists other ingredients in bypassing the skin’s outermost barrier. This mechanism is particularly effective for maximizing the benefits of water-soluble actives like Sodium Hyaluronate. Because the ingredient is highly water-soluble, it prevents the “tacky” feeling often associated with high-concentration serums.Consistency and stability are significantly improved by its presence in emulsions. As a liquid-to-wax polymer, it helps bridge the gap between oil and water phases, ensuring that textures remain uniform over time. Its inert chemical nature means it rarely reacts with other components, making it a reliable choice for stabilizing complex anti-aging or brightening complexes.
Broader Applications & Origins
While widely used in facial serums and moisturizers, this ingredient also appears frequently in haircare and pharmaceutical ointments. In haircare, it functions as a conditioning agent that adds slip to detangling sprays and shampoos. In medical settings, it often serves as the base for topical treatments because it does not interfere with drug efficacy and is easily washed off with water.
Routine Integration
- Synergies: Works exceptionally well with other humectants like Glycerin and Propanediol to create a multi-level hydration system. It also complements exfoliating acids such as Salicylic Acid by providing a hydrating buffer that reduces irritation.
Clinical Consensus & Safety
The Cosmetic Ingredient Review (CIR) Expert Panel and the European Commission (CosIng) categorize PEG-18 as safe for use in cosmetics. Extensive toxicological evaluations confirm that polyethylene glycols are non-genotoxic and possess a very low potential for skin sensitization. While a historical concern existed regarding impurities like 1,4-dioxane, contemporary cosmetic manufacturing uses vacuum stripping and purification stages to ensure the final ingredient meets strict safety limits. Clinical studies published in PubMed highlight its utility in dermatological preparations for psoriasis and dry skin due to its excellent tolerability and emollient properties.
Is PEG-18 safe for acne-prone skin?
Yes. PEG-18 has a comedogenic rating of 0, meaning it does not clog pores. Its water-soluble nature ensures that it provides hydration without the greasy residue that typically triggers breakouts in oily skin types.
Why do some people avoid PEG ingredients?
Concerns usually stem from potential manufacturing impurities like 1,4-dioxane. However, cosmetic-grade PEG-18 is highly purified to remove these traces, and regulatory bodies like the SCCS maintain that it is safe for topical application in standard concentrations.
Can PEG-18 be used on sensitive skin?
Generally, yes. It is considered a low-irritation ingredient. However, individuals with compromised skin barriers or known PEG allergies should perform a patch test, as rare cases of contact dermatitis have been documented in extremely sensitive individuals.